Asobo confirmed the bug a some time ago here: WEIGHT and BALANCE Menu BUG - #4 by SnowedTome73
It’s unchanged since then. We all want this.
Users have been asking for missions to edit payload stations as avatars and objects enter/leave the aircraft, but this bug prevents the sim from being sensible for a casual user that relies on the sim dialogs, so we’ve held off on this logic.