I normally setup a bunch of variable names to hold my common measurements and then need to apply particular named measurements to features.
At the moment there is no autocomplete in the Sketch Dimension dialog. It would be great if you could use Tab / Space or some combination of CTRL+Space etc to get the dialog to autocomplete as much of the variable name as possible.
Something similar to the autocomplete on your typical linux command line interface.
Right now you need to remember exactly what the variable name was and type it out completely until you are lucky and get everything in black lettering to let you know you have it right, and when you have a lot of different variables, that is very difficult.
Good luck with your product. I think it is coming along really well and I look forward to seeing future revisions.
Regards
Craig.