I would like to program my own custom set of modules and would like to know if I can use the back bus to hardwire connections between my modules? In other words: Is there an addressable “array of variables” that is shared between modules? If yes, how do I address it?
It’s just an image. To pass data between modules you need to use the expander functionality and have the modules placed next to each other or use shared resources.
I have made a limited run of custom connectors for these which I am selling for $50 a piece 
really? can you post a link?
He is joking
Oh, … insight about me: I am bad with sarcasm in written form.
does the expander functionality work up / down as well or just side to side?
Just side to side