As I mentioned in this thread: Desktop new design is nearly ready, please cast your final vote!, I have been playing around with how the new design could be implemented to make it more easily theme-able.
In this repo, I have implemented the new design in CSS and HTML. Everything in structured around CSS variables, so simple color / font / size changes should be straightforward.
Notes: I tried to use existing class names and structure where possible. I added new classes where I thought it helped. I tried to stay true to the new design as much as I could, although I used the existing icons for simplicity and added back in indentation. I also created a few example themes.
I don’t feel confident implementing this in the current Joplin codebase, but my hope is that it is helpful to others as a starting point.
Kudos to the designer who created the original mockup!
Base theme, in CSS
Dark mode example
Note: there are couple more theme examples in the repo