I would like to be able to use User Waypoints directly in the FMS of my aircraft.
For example there are special military approach procedures (mostly for VFR) which have their own waypoints. I created them inside of the Navigraph Charts app for some airports and it would be really great to use them in the MCDU or other ingame navigation devices like the Garmin GPS.
You can create user waypoints in an FMC/MCDU based on bearing and distance from an existing waypoint e.g WYPT260/5. The format depends on the aircraft. Boeing typically uses FIXBRG/DST, Airbus typically FIX/BRG/DST
There are many videos on the internet showing this by searching “How to enter user defined waypoint into FMC”.