How do I merge WooCommerce categories with the same name?

You can try using Term Management plugin. You can use it to bulk merge your duplicate categories into one. Follow these steps:

  1. Install and activate the plugin.
  2. Go to Posts > Categories.
  3. Select the categories that you want to merge. Then select the merge
    option from the bulk option.
  4. Type the name to which you want to merge these categories. Finally,
    click on the Apply button.