I really want to be able to filter on the PLANNER. (There is no Category for Planner) At the very least I want to be able to toggle closed tasks on or off like the List view. When I mark a task complete in the Planner, it stays there greyed out with a nice green icon, but if i close the planner and re-open, closed tasks are gone. It would be super useful to be able to toggle "view closed" tasks and subtasks on and off.

You can toggle to show Closed Tasks in Calendar views, but this is not available in Planner. I work across multiple Spaces and Lists and I need to allocate my tasks in the Planner so I don't overlap even if I'm in different Spaces.