I was originally intending to ask if multiple engineering console RCS Accelerators (+ turn rate strength) stacked.
That's when I got to thinking: does the boff space trait Efficiency stack?
And then, finally, I realized that would probably be best to ask: what stacks and what doesn't? Stacking mechanics as a whole in STO are not to well documented, whether it's consoles, boff traits, debuffs, etc etc.
Ok first I know Efficiency stacks. As to what else stacks it gets a little shady but here is what i know from personal testing.
Damage consoles stack, I have 3 +26% consoles, however they dont stack on each other, instead each adds a set number which is 26% of the base damage of the weapon. I would assume other +% consoles work the same way.
I have been told that +x.x to y, ie +3.5 to shield power, consoles stack with diminishing returns but I have not personally done any testing with this.
RCS consoles do stack but yes, with diminishing returns. I dont know the exact amout that gets dropped off each additional console but a second and third 32% turn rate console will not give you that much. though it does help regardless.