No, that's not what I meant. I was looking for a way to change default, predefined baseline--what is essentially the "zero" value. In any case, I ended up solving my own issue. It's funny that I never noticed this before .......

adjusting the arrows seem to do what I want. I just don't know how each arrow is supposed to affect the expressions. The far right arrow doesn't seem to do anything while the other three move objects. Is there more to this?

Quoting the online manual:

• Dragging the leftmost triangle up or down moves the baseline for these expressions vertically, affecting the entire piece.
• Dragging the second triangle sets the baseline for expressions for this staff only.
• Dragging the third triangle, whose effect is only visible in Page View, sets the baseline for this staff in this system only.
• Dragging the rightmost triangle sets the baseline for the next expression you enter.

You can see it for yourself here:

https://usermanuals.finalemusic.com/FinaleWin/Content/Finale/Expressions.htm 

(Go to the section “To adjust the vertical positioning of expressions on a baseline”)

Thanks Peter,

I feel so ashamed of myself ...... ha