The "Errors / Variations" tab on a set is simply meant to show the cards that appear twice (or more) in a checklist.
If there is an ERR, then by logic there must be a COR, meaning there are two of that card in the checklist. Same with VARs - you cannot have a stand-alone VAR, it has to have a partner card.
Seeing each specific card that is classified as a UER can be accomplished by going to the "Glossary" tab, but since they only exist as a single card in the Database, they won't populate on the "Errors / Variations" report in a given set.
I'll never quit collecting entirely, but I am downsizing. Check out my COMC store and help me thin out what I don't want so I can buy cards that I do want. See something you like? Send me a message on here, and we can knock the price down quite a bit. I'll even take a bit of a loss if it means getting you a card you really want.