Hello Gouckieha32
If the SBB timetable is suggesting this itinerary, you can trust on it. SBB would not suggest a trip which is not doable. We Swiss do like efficency, any train change that is more than 3 minutes is not causing headache with us. A Swiss would be worried if the change is 2 minutes, a 6 minutes change is definitely nothing to worry about.
Lausanne is an easy train station to navigate, and changing trains is therefore easily doable. For sure, you won’t be the only ones doing this transfer. In the unlikely event of a train delay, SBB will rebook you free of charge.
However, holding a normal point-to-point ticket from Geneva to Lausanne, you are welcome to use any train serving this line; you are not forced to use the train as given by the SBB trip planner (unless you use Supersaver tickets). Simply board a train that leaves Geneva 30 minutes earlier, and you will have plenty of time in Lausanne to make the change.
Kind regards,
Roland