Task: Merge data for multiple executions

n8n workflow JSON:
{"nodes":[{"name":"On clicking 'execute'","type":"n8n-nodes-base.manualTrigger","position":[270,330],"parameters":{},"typeVersion":1},{"name":"Merge Data","type":"n8n-nodes-base.function","position":[1230,430],"parameters":{"functionCode":"const allData = []\n\nlet counter = 0;\ndo {\n  try {\n    const items = $items(\"RSS Feed Read\", 0, counter).map(item => item.json);\n    allData.push.apply(allData, items);\n  } catch (error) {\n    return [{json: {allData}}];  \n  }\n\n  counter++;\n} while(true);\n\n\n"},"typeVersion":1},{"name":"Function","type":"n8n-nodes-base.function","position":[470,330],"parameters":{"functionCode":"return [\n  {\n    json: {\n      url: 'https://medium.com/feed/n8n-io',\n    }\n  },\n  {\n    json: {\n      url: 'https://dev.to/feed/n8n',\n    }\n  }\n];"},"typeVersion":1},{"name":"RSS Feed Read","type":"n8n-nodes-base.rssFeedRead","position":[870,330],"parameters":{"url":"={{$json[\"url\"]}}"},"typeVersion":1},{"name":"SplitInBatches","type":"n8n-nodes-base.splitInBatches","position":[670,330],"parameters":{"options":{},"batchSize":1},"typeVersion":1},{"name":"IF","type":"n8n-nodes-base.if","position":[1070,520],"parameters":{"conditions":{"boolean":[{"value1":true,"value2":"={{$node[\"SplitInBatches\"].context[\"noItemsLeft\"]}}"}]}},"typeVersion":1}],"connections":{"IF":{"main":[[{"node":"Merge Data","type":"main","index":0}],[{"node":"SplitInBatches","type":"main","index":0}]]},"Function":{"main":[[{"node":"SplitInBatches","type":"main","index":0}]]},"RSS Feed Read":{"main":[[{"node":"IF","type":"main","index":0}]]},"SplitInBatches":{"main":[[{"node":"RSS Feed Read","type":"main","index":0}]]},"On clicking 'execute'":{"main":[[{"node":"Function","type":"main","index":0}]]}}}