Setting up expression maps for a complex library like the Orchestral Tools Berlin Orchestra can (actually, will) take a long time. Creating each instrument’s expression map from scratch each time is also prone to error.
As far as I can tell, there is no way to copy individual or multiple base and add-on switches from one expression map to another. While it is possible to duplicate and then edit an entire expression map, this is often inefficient and difficult to do. For example, the expressions are listed (with a few exceptions) in alphabetical order in Dorico. This is typically not the case with the articulation order in, say, the Sine Player for an OT orchestral instrument. It is therefore very hard to visually match OT articulations to base switches as a result.
Among the things that can be done to make this job faster and less error-prone (for the expression map creator, at least) is to allow copy and paste of multiple base and add-on switches from one expression map to another.
Perhaps a lot of coding (or revising of coding) is required to allow copying and pasting of individual and multiple base and add-on switches. However, I do think that enabling such capability would enable all of us to create expression maps with more speed and ease.