Вопрос: Как в Gutenberg создать обертывающий блок, и добавлять внутрь него контент?

Лучший ответ:
Варианты/примеры обертки дефолтных/кастомных блоковadd_filter('render_block','wrapBlock',10,2);
function wrapBlock($block_content,$block){
	$name=$block['blockName'];
	if($name){return sprintf('<div class="e-block e-block-%s">%s</div>',str_replace('/','-',$name),$block_content);}
	///if($name){return sprintf('<div class="easdasdas">'.$block_content.'</div>'}
	// if($name){
		// $content='<div class="vabtopic">';
		// $content.=$block_content;
		// $content.='</div>';
		// return $content;
	// }
		// if($block['blockName']==='core/paragraph'){
		// $content='<div class="wp-block-paragraph">';
		// $content.=$block_content;
		// $content.='</div>';
		// return $content;
	// }elseif($block['blockName']==='core/heading'){
		// $content='<div class="wp-block-heading">';
		// $content.=$block_content;
		// $content.='</div>';
		// return $content;
	// }
	// if($name=='core/html'){
		// $Block='<span class="core__html">'.$block_content.'</span>';
		// return sprintf($Block);
	// }else if($name=='core/paragraph'){
		// return sprintf('<span class="core__paragraph">'.$block_content.'</span>');
	// }
	return $block_content;
}
примеры создания блоков гута:переменныеvar GutCal=VAB_Gut_In.Gut_Cal_Out,el=wp.element.createElement,registerBlockType=wp.blocks.registerBlockType,blockStyle={backgroundColor:'#900',color:'#fff',padding:'20px'},RichText=wp.editor.RichText,components=wp.components,i18n=wp.i18n,MediaUpload=wp.editor.MediaUpload;Не редактируемый блокregisterBlockType('vabtopic/vab-calendar',{
	title:GutCal,
	icon:{background:'#000',foreground:'#ffff00',src:'calendar',},
	category:'VAB_category',
	edit:function(props){return el('input',{className:props.className+' VAB_Calendar',type:'text',name:'VAB_Calendar'});},
	save:function(){return el('input',{className:'VAB_Calendar',type:'text',name:'VAB_Calendar'});},
});Редактируемый блокregisterBlockType('vabtopic/vab-text',{
	title:'text',
	icon:{background:'#000',foreground:'#ffff00',src:'universal-access-alt',},
	category:'VAB_category',
	attributes:{content:{type:'array',source:'children',selector:'p',},},
	edit:function(props){
			var content=props.attributes.content;
			function onChangeContent(newContent){props.setAttributes({content:newContent});}
			return el(RichText,{tagName:'p',className:props.className,onChange:onChangeContent,value:content,});
		},
	save:function(props){
		return el(RichText.Content,{tagName:'p',value:props.attributes.content,});
		},
});InnerBlocks - блоки внутри блока, где allowedBlocks массив добавляемых блоковvar InnerBlocks=wp.editor.InnerBlocks,allowedBlocks=['vabtopic/vab-text','vabtopic/vab-calendar','vabtopic/vab-mixed-block'],icon=el('svg',{width:24,height:24,stroke:"red"},el('path',{d:"M 0.71578,2 C 0.32064,2 0,2.3157307 0,2.7060291 V 21.294175 C 0,21.683751 0.32064,22 0.71578,22 H 23.28422 C 23.67936,21.999999 24,21.68375 24,21.294174 V 5.9812162 2.7060291 C 24,2.3157307 23.67936,2 23.28422,2 Z M 1.43136,3.411854 H 22.56864 V 5.9812162 H 1.43136 Z m 15.96822,0.4609128 c -0.46106,0 -0.83495,0.3687886 -0.83495,0.8235651 0,0.4549561 0.37389,0.8237674 0.83495,0.8237674 0.46124,0 0.83494,-0.3688113 0.83494,-0.8237674 0,-0.4547765 -0.3737,-0.8235651 -0.83494,-0.8235651 z m 2.78339,0 c -0.46124,0 -0.83515,0.3687886 -0.83515,0.8235651 0,0.4549561 0.37391,0.8237674 0.83515,0.8237674 0.46106,0 0.83494,-0.3688113 0.83494,-0.8237674 0,-0.4547765 -0.37388,-0.8235651 -0.83494,-0.8235651 z M 3.65005,3.990507 c -0.39514,0 -0.71557,0.316068 -0.71557,0.7058249 0,0.3899364 0.32043,0.7060281 0.71557,0.7060281 h 8.92617 c 0.39533,0 0.71579,-0.3160917 0.71579,-0.7060281 0,-0.3897569 -0.32046,-0.7058249 -0.71579,-0.7058249 z M 1.43136,7.3930022 H 22.56864 V 20.588214 H 1.43136 Z m 7.89453,1.5110662 c -0.16452,0 -0.32898,0.05577 -0.46246,0.1672098 -0.53833,0.4497184 -4.5418,3.7936988 -5.09862,4.2587688 -0.30157,0.251951 -0.33909,0.697517 -0.0837,0.994982 0.25543,0.297464 0.70697,0.33447 1.00873,0.08252 l 0.0299,-0.02491 v 3.282584 H 3.93296 c -0.39533,0 -0.71579,0.316024 -0.71579,0.705961 0,0.389937 0.32046,0.706028 0.71579,0.706028 h 16.13408 c 0.39533,0 0.71579,-0.316091 0.71579,-0.706028 0,-0.389937 -0.32046,-0.705961 -0.71579,-0.705961 h -1.57797 v -1.656765 h 1.04279 c 0.4801,0 0.82469,-0.458384 0.68462,-0.911716 L 18.45791,9.4042733 c -0.20526,-0.6650049 -1.16379,-0.6650049 -1.36924,0 l -1.75836,5.6924727 c -0.14007,0.453151 0.20415,0.911716 0.68462,0.911716 h 1.04278 v 1.656764 h -3.1256 v -3.282584 l 0.0299,0.02491 c 0.30176,0.251951 0.7533,0.214945 1.00873,-0.08252 0.25543,-0.297465 0.21792,-0.743031 -0.0837,-0.994982 C 14.37068,12.898749 10.59208,9.7426047 9.78843,9.0712782 9.65494,8.9598418 9.49041,8.9040684 9.32589,8.9040684 Z m 0,1.6310446 3.17472,2.651678 v 4.478436 h -0.99242 v -3.38553 c 0,-0.389937 -0.32043,-0.706028 -0.71558,-0.706028 H 7.85924 c -0.39533,0 -0.71572,0.316091 -0.71572,0.706028 v 3.38553 H 6.15103 v -4.478436 h 2.1e-4 z m 8.4474,1.497088 0.79229,2.564476 h -1.58437 z m -9.19848,2.953457 h 1.50202 v 2.679569 H 8.57481 Z"}));
registerBlockType('vabtopic/custom', {
	title:'Мой кастомный блок',
	icon:icon,
	description:'Мой Custom Section',
	category:'VAB_category',
	edit:function(props){
		return(el('div',{className:props.className},el(InnerBlocks,{allowedBlocks:allowedBlocks,})));
	},
	save:function(props){
		return(el('div',{className:props.className},el('div',{className:'vab_custom_section'},el(InnerBlocks.Content,null))));
	}
});InnerBlocks  редактируемый (Ваш вопрос)registerBlockType('vabtopic/custom', {
	title:'Мой кастомный блок',
	icon:icon,
	description:'Мой Custom Section',
	category:'VAB_category',
	edit:function(props){
		var content=props.attributes.content;
		function onChangeContent(newContent){props.setAttributes({content:newContent});}
		return(
			el('div',{className:props.className},
					el(RichText,{tagName:'p',className:props.className,onChange:onChangeContent,value:content,}),
					el('div',{className:'vab_custom_section'},el(InnerBlocks,{allowedBlocks:allowedBlocks,}))
				)
		);
	},
	save:function(props){
	return(
		el('div',{className:props.className},
			el(RichText.Content,{tagName:'p',value:props.attributes.content,}),
			el('div',{className:'vab_custom_section'},el(InnerBlocks.Content,null))
		)
	);
	},
});Смешанный пример(шаблон чего-то)registerBlockType('vabtopic/vab-mixed-block',{
	title: i18n.__('Смешанный блок','VAB'),
	icon:'index-card',
	category:'VAB_category',
	attributes:{
		title:{type:'array',source:'children',selector:'h2',},
		mediaID:{type:'number',},
		mediaURL:{type:'string',source:'attribute',selector:'img',attribute:'src',},
		mixedfirst:{type:'array',source:'children',selector:'.mixedfirst',},
		mixedsecond:{type:'array',source:'children',selector:'.mixedsecond',},
	},
	edit:function(props){
		var attributes=props.attributes;
		var onSelectImage=function(media){
			return props.setAttributes({mediaURL:media.url,mediaID:media.id,});
		};
		return (
			el('div',{className:props.className},
				el(RichText,{tagName:'h2',inline:true,placeholder:i18n.__('Заголовок'),value:attributes.title,onChange:function(value){props.setAttributes({title:value});},
				}),
				el('div',{className:'recipe-image'},
					el(MediaUpload,{onSelect:onSelectImage,allowedTypes:'image',value:attributes.mediaID,
						render:function(obj){
							return el(components.Button,{
									className:attributes.mediaID?'image-button':'button button-large',
									onClick:obj.open
								},
								! attributes.mediaID?i18n.__('Загрузка изображения'):el('img',{src:attributes.mediaURL})
							);
						}
					})
				),
				el('h3',{},i18n.__('Редактируемый блок первый')),
				el(RichText,{tagName:'ul',multiline:'li',placeholder:i18n.__('placeholder'),value:attributes.mixedfirst,
					onChange:function(value){props.setAttributes({mixedfirst:value});},
					className:'mixedfirst',
				}),
				el('h3',{},i18n.__('Редактируемый блок второй')),
				el(RichText,{
					tagName:'div',
					inline:false,
					placeholder:i18n.__('placeholder'),
					value:attributes.mixedsecond,
					onChange:function(value){
						props.setAttributes({mixedsecond:value});
					},
				})
			)
		);
	},
	save:function(props){
		var attributes=props.attributes;
		return(
			el('div',{className:props.className},
				el(RichText.Content,{tagName:'h2',value:attributes.title}),
				attributes.mediaURL&&el('div',{className:'mixed-image'},el('img',{src:attributes.mediaURL}),),
				el('h3',{},i18n.__('Редактируемый блок первый','VAB')),
				el(RichText.Content,{tagName:'ul',className:'mixedfirst',value:attributes.mixedfirst}),
				el('h3',{},i18n.__('Редактируемый блок второй','VAB')),
				el(RichText.Content,{tagName:'div',className:'mixedsecond',value:attributes.mixedsecond}),
			)
		);
	},
});
в этот блок по аналогии можно запихать так же InnerBlocks
Не пытаемся в InnerBlocks запихать core/freeform (классический блок) 
при регистрации js указываем зависимости необходимых элементов/библиотекwp_register_script(...array('wp-editor','wp-blocks','wp-i18n','wp-element','wp-dom-ready','wp-edit-post','wp-components'));

Худший ответ:
Решение:( function( blocks, element, blockEditor ) {
	let el = element.createElement;
	let InnerBlocks = blockEditor.InnerBlocks;

	blocks.registerBlockType( 'gutenberg-custom-block/section', {
		title: 'Section', 					
		description: 'section description', 
		category: 'layout', 				
		keywords: 'section', 				
		icon: {
			background: '#7e70af',
			foreground: '#fff',
			src: 'book-alt'
		},

		edit: function( props ) {
			return el(
				'section',
				{ className: props.className},
				el( InnerBlocks )
			);
		},

		save: function( props ) {
			return el(
				'section',
				{ className: props.className },
				el( InnerBlocks.Content )
			);
		},
	} );

} (
	window.wp.blocks,
	window.wp.element,
	window.wp.blockEditor,
) );На выходе получаем: <section class="wp-block-gutenberg-custom-block-section">
    <!-- ТУТ ВЛОЖЕННЫЕ БЛОКИ -->
</section>Подробнее читайте тут