Sorry, I don't have Index controllers, so I can't test this. My only suggestion would be to check in the Steam controller bindings that the "GrabGrip," "GrabPinch," and "InteractUI" actions are each associated with some input.
Thanks for the hint.
I had to search a bit to find the options and if I looked right it´s already set up properly. But I was in a hurry and now I´m a t furality. I´ll try again later with more time. If I can reach something I´ll tell you.
I´m absolutely hyped for any VR games, wheter I can get them running or not, especially if they try interesting mechanics like this.