Opening doors, hatches and sometimes windows.
An in-flight map that showed Navaids, frequencies, airspace.
A Navlog that showed legs of routes, VOR Frequencies, etc.
A Fuel Burn calculator (okay, this one not in FSX but i’m not asking for much here).
Ability to easily switch planes or jump to a different airport.
Instant Replay.
Further VC zoom.
Remove a cloud layer.
Inject fog with a specific base layer altitude for approaches to minimums.
A Pause that PAUSED.
A more classic style menu that uses the ALT key for quickly accessing the menu.
The ability to change your flight plan without having to exit your flight!
Correct Taxiway names.
Taxiway lights that are on the edge of the taxiway rather than the middle of it.
An interface that remembered my filters and settings.
Seriously… all things FSX has - you know, the simulator that MSFS was supposed to be the ‘continuation of’ in the MS Flight Sim series- yet somehow carried over none of the features…