Expression Map - Helpful Additions

I’m new to Cubase and maybe I’m missing something, but how about adding the ability to change a controller by a (±)% on a particular channel instead of having to pick a hard value. In other words, I may want to change the characteristics of a note slightly by adding the articulation instead of picking hard numbers for everything. I know it can be done manually in the controller lanes but so can all the rest of expression mapping.