If I understand you correctly - Do you want to output a DMX channel at a particular level over artnet for each preset that is played?

You can do this using PixelMad

Use 1 layer with a white square (lib0 file 0 or 4) and send it to a very small mix window on output 1
Then patch one pixel intensity in pixelmad that maps over the top of the very small mix window with the white square
As you adjust the intensity level of the layer with the white square, this will change the DMX output level from 0-255

You can program this in with each preset to give a different level for each preset that is played.

S