Yes I understand your goal. In which theme default is it set to 15%? Is the default Icons-Grey theme 15%?
I haven’t yet started to use the software, I have only the one image that I have been using as I am going through the manual page by page to learn before I switch to darktable.
I felt that a combo of the ctrl+b and 15% would be the ideal workspace.
While working with this image, it looked right until I would ctrl+b. Then I would clearly see it needed more exposure. With the grey background it was so hard for me to clearly read on the histogram, hence it’s now black. I felt that if ctrl+b was on all the time, I would be far more productive. On a 40" screen there is plenty of real-estate to do this. It still leaves me with a 27" image.
I don’t know if 150 wide border is the right amount of white to be working with though.
I can read the fonts better if they are 0% on 15% background. Not really an issue when fonts are bold though.
Update:
I now changed the overall background grey to closely resemble 18% as found when using ctrl+b
Here is the code… @define-color bg_color @grey_55;