hi hungary man,
there was a post about this a while ago but cannot find it rn. (see below)
you can do pretty much what u r describing if you drop in as many 1-ch Generic Dimmer fixtures into your fixture patch as the number of chans you want to test, assign a tag to (up to 16 of) them. switch to Abletone and pop in a Generic device and set all (or as many as the number of chans you wanna test, up to 16) of its param slots to dim. each Generic dial now controls a single DMX channel. if you need to test more than 16 chans at a time, just add more Generic Dimmers and use an additional tag & Generic device.
EDIT: here’s the post that describes this:
EDIT2: reverse google image searching image of your fixture also often yields useful results.