I would like to have my Dynamics (pp, ff, etc. from the Dynamics section of the Scoring Inspector) to be defaulted to size 36 (instead of 48). Any way to do this across projects?
I also would like 
Not possible at this time (AFAIK).
You can set each dynamic symbol individually to a size that will be remembered in the current project. But, those sizes will be reset to default (48) after Cubase restart.
The best I have come up with is to add all the symbols in a pile on the score, select them all, and change their size collectively. At least it gets it all done at once…when added later the symbols are all 36.
This is exactly what I do.
Cumbersome, and somewhat ridiculous, I must admit.
I have requested long ago new entries in Score Settings>Project>Font to set and edit Dynamics, as well as Expression Maps font size for the whole score. Still hoping for their addition.
Agreed, a bit ridiculous, but on the other hand it turns my score into an interesting conceptual art piece (at least for the time while the pile up of dynamics is there).