I have noticed with Maximon Solutions that once you have applied filters at Campaign Activity level to your contact list, even though you have the ability to 'untoggle' them, it does not actually revert the contact list back to its original.
See loom video where I have created a contact list, added it to the campaign activity, applied my filters (you can see the number of contacts have changed), then changed my mind and unapplied the filters and you will see the contact list number stays exactly the same, it does not revert back to what it was.
Video from Maximon Solutions CRM:
https://www.useloom.com/share/d5b71d850d414a1b8ee6131fd689dbbd
Filters remove contacts from a campaign activity and prevent them from being added. We don't however store the reports etc. that are used to populate the activity and therefore are unable to add them again.
We could look at changing the way campaign activities work so that the list is dynamic based on a report rather than adding contacts as a one-off.
Could we consider renaming it from 'Filters' to something else? It doesn't really act like a filter would on a Report because it doesn't store the report info, so I think Filters is the wrong term for this.
Instead of the toggles (which imply you can turn them on and off, which you can't), could it just say 'Apply' and then go grey/non-clickable when it's been pressed so people know they can't change them?