When flying in a group multiplayer session friends can be seen on the world map but not on the VFR map or TACS display on the Garmin while Live traffic can be seen on these maps/displays. Note that players aircraft are visual in sim.
This was observed by both parties.
Settings are as follows:
Multiplayer: OFF
Air Traffic: LIVE Traffic
Weather & Time: LIVE
Aircraft: Carenardo M20R Ovation & Beechcraft Bonanza
Location: YCFS, YPMQ, YSCO YSTW & YARM
Hi @vk2ams,
I’ll answer your post since no one has. 
TACS in it’s current development only shows “Live Traffic”. So anything outside of this, isn’t implemented.
However, there is a post in #self-service:wishlist for TCAS that you can contribute to and up vote.
https://forums.flightsimulator.com/t/tcas-live-players/312363
I could not find a topic in wishlist for Group players showing on TCAS.
Regarding seeing friends on the “VFR” (in-game) map, this is also not implemented. I couldn’t find a topic in wishlist for that, so you could create one.
Since both of these items you have posted are not bugs, but rather the current way MSFS is designed, it is best to use the wishlist. Up vote the existing one in wishlist then create a new topic for the in-game VFR and another one for the Group TCAS.