Thanks for the quick reply! Didn't think the check launchpad.

In the meantime, for those that need it, I remembered a quicker way to delete all the OPF format books in bulk, instead of individually. I do a search on the format=OPF, finding all books with that format, highlight all those books found, right click, and then click on remove books of a specific format. You can then choose to remove the OPF formats only.
Be careful when using this, because you can delete more than just the OPF files if you choose wrong.