I was notified today when opening QB2021 that there was an update available, which listed itself as R12. Updating to this version finally fixed the extraneous empty tabs issue that had been going on before.

In the update window, there is a link to click on to get the changelog; unfortunately, the page it links to has still not been updated since R10's release, and so all information regarding the R11 and R12 updates are not present on that page.