There are dedicated fast lanes also at transit but usually noone checks access. I've had situations where all passengers were queuing in the fast lanes and noone in the regular Y lane. Probably the late comers didn't read the signs and just stood in line behind all the others already there. So I whisked through the Eco lane.

If it's too much of a zoo and you see plenty of people with Y boarding pass and that otherwise don't look/smell like Plats or Gold (but beware: looks can be misleading) in the fast lane just walk up to the security people, be humble / don't take a DYKWIA attitude, pretend to be looking for the priority lane while showing your F/J boarding pass or FFP card and ask politely where to go because you have a short connection, and they'll usually let you through.