here is what you do:
First, you define your pixel. It will be a new, top level geometry:
this is the model pixel
You define it as a Beam:
Then you go to the DMX and add DMX channels for this pixel, only once:
Then, you go back to the geometry tree and add this pixel to your geometry tree (Add child geometry) as a reference:
and you add it as many times to the geometry tree as many pixels you want to have... essentially, you define it once and then keep clicking the Duplicate selection, or use the Multiple duplication and enter how many pixels you want to add:
(Here, i added it 4 times). Now you adjust the x and y of each of the referenced pixels1,2,3,4... you must do this manually for each pixel. You will also now define the DMX offset for each pixel: Imagine that this pixel is controlled by RGBW, that is 4 channels. So when you are editing these referenced pixels, edit not only x, y, but also edit the address offset, alway adding 4 to the previous one. First reference will be at 1, second at 1+4=5, next one at 9, next at 13...:
Now, if you look at the Summary tab, you can see that we now have four pixels, each with 4 channels.
This way allows us to have a nicely defined pixel and dmx channels for it, then just reference it as many times as needed. You can change the beam properties of the original Pixel in one place and it is used by the references. The Luminous Flux (if you add this value) of this pixel should be a value of the real individual single pixel. We can now also adjust DMX channels in one central place and these again, are used by the referenced pixels.
The file i used for screenshots is attached here.
Hope this helps