Master Server Multiple sessions???

Okay I know UE4 got steam subsystem that works with the blueprint nodes
Find session
Create Session
host session
destroy Session

But if I wanted to host a mobile game??

I know that getting the engine from Git can let me compile a server version, but as far as I have read that will only create and host One full authoritative Session.

Is this really the case then how do you make a network like most games Example
Friends online list Invinte chat system but do not see characters only messages and join party

then able to create a session and join matchmaking to pair with other

How do you do every player is on their own Room.
Something like photons flow

Connect to Master Server
Create or Join Room

Please i dont need examples I just need like the information where i can search this information as i know networking is very game by game varies cases

You can use this solution to to run a master server on Windows / Linux and get a list of game servers using the UE4 plug-in.ā€¦server-listing