Supplement feeds in Google Merchant Center are great for adding or editing data that is not available in the primary feed. Allowing you to setup strategies or enhancing your Google Shopping setup.
But how do you remove this feed? It does not allow me to do this?
That is because you are still linking the supplement feed to a primary feed.
Go to Google Merchant Center > Products > Feeds > click on your primary feed it is connected to.
Now select from the tabs Feed Rules and click on the feed rule that says Take from: (supplement feed)
Now hover over the rule and click on the delete icon.
You can now save as draft.
Now you will be redirected back to the feed rules, and you can apply the changes.
Go back to the feeds overview, you can now delete your supplement feed.