I just finished a run through the campaign and when I start I set a pretty basic loot filter. Following some suggestions I wanted to show all +level of skills so i could shatter in case I needed them in the future. So I made a new rule to recolor, marked specific affixes and typed level on the search bar, i got the 5 classes names and under them all the +level to skills, so I clicked the checkbox next to the classes names and was done.
I was surprised to note than even if you can only see the level affixes filtered by your search bar when you click the checkbox of the class all class specific affixes get selected, not only the ones that are filtered by the search bar.
So my suggestion is to change the way it works so when you check one of the main categories, the filter in the search bar is also taken into account. A rule that could have been 5 clicks (1 for each class) is needing 100+ clicks, one for each independent +class affix.