Setting up runways in FMB?

[Ataros]

Isn't it possible to create several runways for one airfield and put takeoff waypoints for different groups on top of different runways?

Airfield points are where aircrafts spawn when 'parked' is checked. You can create as many of them as needed. You have to assign a key to "Branch" them in Game Controls Settings Menu in Builder section (exit FMB and go to game settings to do so). Put at least 2 AFPs inside a runway to let AI taxi to the runway from AFPs before takeoff.