Thanks for your hints. I was able to get a good sounding wah sound.
The remaining problem is simply the wah pedal on the Behringer FCB 1010.
I calibrated it (again) but it does not show any reaction for the first 50% of the pedal range.
I do use the Uno4Kemper chip but the different curves do not show any improvement.
How do you use your 1010 wah pedal? What curve?
I had a similar problem. In my case this has been a mechanical adjustment issue regarding the red LED which is part of the optoelectrical module within the FCB reading the foil stripe connected to the pedal. Since I repositioned the red LED a bit, I've now activity across the whole mechanical pedal range.