For items in collection, I use it to note specific details such as for Sega Genesis or Master System games, I will put if it has a hangtab. For PC CD-ROM games that originally come in boxes, I will check the box for disc/cart, and in notes put "cd and jewel case" to indicate that I have more than the disc, but I don't have the box.
Or I may use it to track a variation on an item, without adding the variation to the database. I will do this for a "minor" variation... example if you look on this page of my collection:
https://vgcollect.com/tripredacus/gen/13You go down to where I have 2 Sonic 2 NFR text label in the list, you should be able to see the notes there. And I use it to note to myself that I have two variations of it, they have different labels and mold stampings...
For wishlist, when I used to put everything there (PC and others), I would put if I needed specific discs. A lot of the time I would buy games at thrift that are multi-disc games, but it would be missing some. So I could put a game on my wishlist and check the box for disc, and in notes put "have disc 1" or "missing game disc" or whatever.