Track Button unresponsive for camera rigs in Sequencer

Hello.
I’m a beginner. I was reading the manual about camera rigs. Whether by drag&drop or right-click, I may import both camera crane and camera rail along with their attached cameras. But clicking their track’s button for keyframing pitch, yaw, current position etc. simply doesn’t produce any track… nothing happens. Starting from scratch doesn’t work, as won’t restarting UE either.
Hint (?): Mac Os Mojave + UE 4.27.
What am I getting wrong? Thank you very much.