"You can select all the dimension lines then increase or decrease their font size.
All the dimension lines use the font selected in the preferences panel."

thank you for your response.

1. most critically, just how does one select all the dimension lines (only)? (ditto rooms, walls, etc)

2. a function like Select All Rooms, Select All Walls, etc, would be helpful

3. Preferences only sets a Font. It is odd and unhelpful that a default size is not also a setting.