Too complicated to explain here but Search & Filtering and Fixture Creator should help. There is also the Windows Fixture Editor and you can also look into the Generic fixtures already in the library where, for example, an LED PAR where ch1 is red, ch2 is green, ch3 is blue and ch3 is intensity will be listed as RGBI.
All of his does, of course, rely on you knowing what parameters your fixtures use (i.e. having access to the manual for the specific model).
If you don't have the manual then proceed as follows...
With an empty patch, assign some dimmers (more than the number of parameters you think the fixture has got) and starting at the fixture's address. With the fixture powered up, try all the "dimmers" and see what happens.
Bear in mind that, to get output, you may need at least two parameters (intensity and colour) up at the same time. You may need three if there is a "shutter" parameter that isn't open at zero.
Try to be methodical but it does involve some trial and error. Good luck!