Добавь в начало кода фильт по подкатегориям и дате публикации (за неделю, месяц, год) с кнопкой "найти" не затранивая исходный код.

<?php
   /*
   Template Name: Reports Category Template
   Template Post Type: category
   */
   ?>
<?php 
   if ( in_category( array(456, 2, 3, 4, 5, 6, 7) ) ) {
   ?>
<?php get_header(); ?>
<div id="fby-main-wrap" class="left relative">
<div class="fby-main-boxed-wrap">
<div class="fby-main-out relative">
<div class="fby-main-in">
<div id="fby-main-content-wrap" class="left relative">
<?php $fby_featured_cat = get_option('fby_featured_cat'); if ($fby_featured_cat == "true") { if ( $paged < 2 ) { ?>
<div id="fby-feat-home-wrap" class="left relative">
   <section id="fby-feat2-wrap" class="left relative">
      <?php
         $category_description = category_description();
         if ( $category_description ) {
             echo '<div class="category-description">' . $category_description . '</div>';
         }
         ?>
   </section>
</div>
<?php } } ?>
<div id="fby-content-body-auto">
   <div id="fby-content-body-wrap" class="home-t33 left relative">
      <div class="fby-content-side-out relative">
         <div class="fby-content-side-in">
            <div id="fby-home-body" class="home-t34 left relative">
               <section class="fby-main-blog-wrap left relative">
                  <ul class="fby-main-blog-story left relative infinite-content">
                     <?php if (have_posts()) : while (have_posts()) : the_post(); ?>
                     <li class="infinite-post">
                        <?php if (  (function_exists('has_post_thumbnail')) && (has_post_thumbnail())  ) { ?>
                        <div class="fby-main-blog-out relative">
                           <a href="<?php the_permalink(); ?>" rel="bookmark">
                              <div class="fby-main-blog-img left relative">
                                 <div class="placeholder220">
                                    <?php the_post_thumbnail('drts_thumbnail', array( 'class' => 'fby-mob-img' )); ?>
                                 </div>
                              </div>
                           </a>
                           <div class="fby-main-blog-in">
                              <div class="fby-main-blog-text left relative">
                                 <a href="<?php the_permalink(); ?>" rel="bookmark">
                                    <h2><?php the_title(); ?></h2>
                                 </a>
                                 <div class="fby-feat1-info">
                                    <span class="fby-blog-date"><i class="fa icon-clock"></i><span class="fby-blog-time"><?php the_time(get_option('date_format')); ?></span></span>
                                 </div>
                                 <p><?php echo wp_trim_words( get_the_excerpt(), 16, '...' ); ?></p>
                              </div>
                           </div>
                        </div>
                        <?php } else { ?>
                        <div class="fby-main-blog-text left relative fby-blog-text-only">
                           <a href="<?php the_permalink(); ?>" rel="bookmark">
                              <h2><?php the_title(); ?></h2>
                           </a>
                           <div class="fby-feat1-info">
                              <span class="fby-blog-date"><i class="fa icon-clock"></i><span class="fby-blog-time"><?php the_time(get_option('date_format')); ?></span></span>
                           </div>
                           <p><?php echo wp_trim_words( get_the_excerpt(), 16, '...' ); ?></p>
                        </div>
                        <?php } ?>
                     </li>
                     <?php endwhile; endif; ?>
                  </ul>
                  <?php if( !is_paged() ){ ?>
                  <?php $fby_infinite_scroll = get_option('fby_infinite_scroll'); if ($fby_infinite_scroll == "true") { if (isset($fby_infinite_scroll)) { ?>
                  <div class="load-more-button-holder"><button class="fby-inf-more-but"><?php esc_html_e( 'Показать больше', 'fishingby' ); ?></button></div>
                  <div class="page-load-status">
                     <div class="loader-ellips infinite-scroll-request">
                        <span class="loader-ellips__dot"></span>
                        <span class="loader-ellips__dot"></span>
                        <span class="loader-ellips__dot"></span>
                        <span class="loader-ellips__dot"></span>
                     </div>
                     <p class="infinite-scroll-last">Нет больше страниц для загрузки</p>
                     <p class="infinite-scroll-error">Нет больше страниц для загрузки</p>
                  </div>
                  <?php } } ?>
                  <?php } ?>
                  <div class="fby-nav-links">
                     <?php if (function_exists("pagination")) { pagination($wp_query->max_num_pages); } ?>
                  </div>
               </section>
            </div>
         </div>
         <?php get_sidebar(); ?>
      </div>
   </div>
</div>
<?php get_footer(); ?>
<?php 
   } 
   ?>