It would be very useful if DO had an option to set the default font:
Setting 1: Use system font
This would use the default operating system font for all elements (toolbars, tabs, tree), but i could define different fonts in the Settings - Prefs - Display - Fonts section individually, or on the toolbars themselves.
Setting 2: Set the default font for DOpus
I could define a font which will then be used by all elements. So i could choose Consolas for example, so all elements of DO would use this font if not defined othervise in Settings or elsewhere.
So if i have a lot of toolbars (well, i have 36 right now), if i dont define the font on a toolbar specifically, it would get the font according to this setting. If i tick Setting 2, all my DO user interface would change to Consolas without having to set each toolbar individually (including tabs, tree and everything).
I use the USB export a lot on different machines because i work in shifts and i dont always get to sit at the same PC, and i use monospace fonts for different reasons. But if i went home and have a custom font downloaded, all i needed to do is change one setting and everything would change to the font i define, instead of setting up every single toolbar.
It only takes a few seconds to do this using the existing UI.
How often do you change the font? How many fonts do you change between?
If the aim is to switch back and forth between a couple font configurations, that's something you could already handle easily enough already using Themes (unless you're a font designer who is using Opus to test a different font each day or something unusual like that).