Is your feature request related to a problem? Please describe.

I've wrote myself an advanced filter to only have groups without the same class, but depending on the number of players I change from looking for already groups who have tank and healer or just groups with a single person in it.

Describe the solution you'd like

I would like to have a store of private filters to select from.

Describe alternatives you've considered

I have a private .txt atm with the different private filters Ive wrote but its annoying to have it open and copy paste all the time

For now, you can use a WoW Macro to change the filter expression. This only changes the advanced expression, not the checkboxes and fields above. See the Public API wiki page.

Is this sufficient for you for now?