It has now been possible for me to record a video with BIAB play back and guitar at the same time. Big step!

But only with MME when I choose Microsoft sound Mapper as output Audio driver.

And I must admit that ASIO sounds much better, but I don't know how to route ASIO to Bandicam.

If I select ASIO and "Analog 1+2 as output port - I can see it playing while in the RME toalmixer window under software playback.

I don't know if its possible to route a software placback to a hardware input. Maybe it can be solved, if I am lucky to find a BIAB user who also has RME.