As much as it pains me to promote someone else's flightsim utility on this forum....
While MSFS group flights are affected by SU6 breaking some of the JFS functionality, I have been recommended a utility to allow MSFS multiplayer group aircraft to be displayed in Little Navmap. Having tried it myself I confirm it works well.
We set up a group flight in MSFS and then used this utility to broadcast our aircraft location, hdg, spd etc into each other's Little Navmap:
https://virtualflight.online/transmitter/