As you (hopefully) know, pressing "w" will select all of your Warp Gates. I need to replicate this behavior for the Refinery, Assimilator, and Extractor, but with "p" instead of "w" and affecting all three types of structures. (Keep in mind that a player might control more than one type of gas structure if an ally leaves in a teamgame.) I don't see any "global hotkey" or similar field/behavior/anything, nor a trigger to assign one. Halp?

I did something similar in my mass game
I made space = select all mass units.
I did this by added all of them to a player group, and have the select trigger just select the group not the unit.

Ah. Two things, though: One, doesn't using keypress detection cause massive lag? Two, I kinda want an icon like the one the Warp Gate has in the lower-right-hand corner. (What would be extremely awesome is if it showed the number of Refineries/Assimilators/Extractors with over 50 energy, sort of like how the Select All Warp Gates icon shows the number which are not in cooldown.)

I have an idea for it. I'll test it out and get back to you.