The menu item "Edit" - "Filter panel" does one thing and a half:
1.) Toggle its own menu item state.
1.5) Show the filter panel (the one below the data), regardless of the state of the menu item.
The "Filter panel" menu item is not capable of hiding the filter panel. The filter panel can only be hidden by clicking the filter panel's "x" button. Hiding the filter panel has no effect on the "Filter panel" menu item state.
HeidiSQL 9.3.0.5104