You can include these in a template, create and save your own custom expression library, or even change your default file(s) if you wish.

Why can't Make Music simply allow users to modify my default expressions regardless of whether a template is being used or not? Or has this happened and I just don't see how to do it?

I'm in a similar situation to David Brinson, however, the proposed "make a template" solution is untenable because I have many expressions that I need to use across a diverse range of documents/instrumentations for which templates aren't my preferred solution.  Yes, I could create a bunch of templates that are close enough to what I might need and customize each new document as needed along the way, but that's creating more work for me instead of fixing something basic that is simply wrong with Finale. Please, please, please add a simple way to customize the default expressions.

… the proposed "make a template" solution is untenable because I have many expressions that I need to use across a diverse range of documents/instrumentations for which templates aren't my preferred solution …

In that case I would save the custom expressions as a library, and then load that custom library into the “diverse range of documents”.

Expressions are document specific (not program specific).

1. Set up a new doc with no libraries

2. Enter all of your custom expressions

3. Save it as a library

You can now add your library to any document. And as always, Peter beat me to it…

John Martilla: "Why can't Make Music simply allow users to modify my default expressions regardless of whether a template is being used or not? Or has this happened and I just don't see how to do it?"

Feel free to vote for versatile library management here:

https://makemusic.zendesk.com/hc/en-us/community/posts/1500000458622-Loading-Libraries-Option-to-merge-add-to-or-overwrite-replace-existing-libraries