I work in Oil & Gas and pretty much every sheet I've ever built has a hidden area at the top where MCF:=1000*ft^3, MMCF:=1000 MCF, bbl:=42*gal, etc. I also have the ideal gas constent, MW of air, and the equation for density in that area since I need that informaiton so often.
That standard hidden area is in a "white board" sheet that I open whenever I want to just do some quick thing that I plan to throw away. If I'm starting something that I might want to keep, I open the whiteboard and rename it.
I tried to define the units (I think it was V13) using the published procedure, but it didn't seem to be worth it.
David