Camera Control - Orbit works with right mouse button, not the left?

Hi everyone. I´m struggling to change the basic camera-orbit system in the standard-project “configurator”.

When I open the Event Graph and go to “Camera Controls” everything seems to be straight forward. The default mode is:

Left Mouse Button + Alt = Start Orbit Cam.

I need to get rid of the “alt” Button for that function. So I disabled the “alt” modifier on the node - fine. But it is still needed to press “alt” one time, for the orbit to work.

When I connect just the “right mouse button”, it works fine.

There is a second Nodesystem, connected to the “alt” button. (“Disable BackgroundBTN while Orbiting Camera”) I dont know what this does, but when I delete it, I can´t Orbit anmore with the left mouse klick.

It seems to me, that the left mouse klick must be somehow “released” into the orbit mode by clicking “left alt”?

Any ideas?

Thanks for helping!
Peter