Unless you put them in a category, they won't appear in a category!!
One way I have found is to get the list to display the earliest date edited. These ones definitely need updating for me, cleaning up after a gedcom import.
For you, a quick look at them could confirm their status - any that don't really need editing much, edit them briefly, and they will go to the 'most recently' edited part of your watchlist. Any ones remaining, you know you have to look at soon.
Margaret