Hi @youbo,
Thanks for the review and feedback as it’s really appreciated.
With regards to categories within Google Merchant centre, Google will always in the first instance assign products to those automatically. Only in very specific cases would Google allow you to assign products to a certain category. You can read more about what those specific instances would be on this page of Google’s website below.
https://support.google.com/merchants/answer/6324436?hl=en-GB
Currently, from what I’m seeing the plugin does not support the optional google_product_category but it may be something that is included in a future update.