Regargeting bug? OR: how do I create a custom rig?

[DrZooDinghy (Mikay²)]

I tried to create a custom rig for animation retargeting for nonhumanoid characters. For this, I clicked “add new” in the retarget manager.
The problem is that nothing happens. Only an empty box opens that says “1 item” but which is empty (see below left).
Is this a bug? Or am I doing something wrong?

[DrZooDinghy (Mikay²)]

OK, I think I found the solution (right after posting my question… )

Right click on skeleton -> create -> create rig