Planner Assignment filter should only show people with assigned tasks in the plan
If you're working in a team with a lot of people, but a specific plan has tasks only assigned to a few people, the Filter functionality should only show people who have tasks assigned in that planner.
Right now filtering by person on a planner attached to a large team is more cumbersome than it needs to be.
I'm surprised this doesn't have more votes. I think it'd be a very important improvement.