title: WooCommerce: change category checkboxes to drop-downs
body: <p>Help me, please!</p>
  
  <p>I need to change the category check-boxes to drop-down on the WooCommerce add product page. The user should be able choose only one category.</p>
  
  <p>When the user chooses a category, all subcategories of the chosen category should be in the next drop-down. The user should be able to choose only one subcategory.</p>
  
  <p>Then I need to put this two drop-downs under "Product Data" drop-down.</p>
  
  <ol>
  <li>How do I remove "Product Categories" block?</li>
  <li>How do I add categories drop-down to the "Product Data" block?</li>
  <li>How do I put subcategories in the second drop-down dependent on the category selected in the first drop-down?</li>
  </ol>
  
  <p><a href="https://i.stack.imgur.com/tQ3ZN.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tQ3ZN.jpg" alt="Categories Image"></a></p>