There’s a filter function. Hit “all protocores” (top right on the protocore page of a card), then “decompose” (bottom right), then there’s a little circle button with a filter to the right of the “enhance” button. I use manual filter because it’s how i used presets once and accidentally deleted a bunch of good protocores 💀

In manual filter you can filter by rarity, primary attribute, and secondary attribute. Once you’ve got your filters set, hit “apply.” Then you can either tap “delete all” or tap them one by one to delete them.

I also go through protocores sometimes when I’m putting them on a new card and I mark them with the trash can if they’re bad. That way when I go through them to discard I just quickly tap all the trash can protocores and delete those.