Hi there, MarkItEmporium.

I appreciate the steps you've tried to remove the deleted tags in QuickBooks Online.

I've got another alternative you can try to resolve this. 

Access your QuickBooks account using a private browser or incognito window and try deleting the tag again. Sometimes, accumulated temporary internet files are the root cause of this unusual behavior. You can use these shortcut keys depending on the browser you're using:

• Google Chrome: press Ctrl + Shift + N.
• Mozilla Firefox: press Ctrl + Shift + P.
• Safari: press Command + Shift + N.

If it works, go back to your regular browser and clear the cache to start the browser fresh, and ensure you're using a supported browser.

I've added some articles modifying and adjusting inventories for additional reference:

• Adjust inventory quantity on hand in QBO.
• Edit an inventory quantity adjustment.

I'll be around if you have additional questions or other concerns navigating your account. Take care!