Preferences GUI still in alpha in the 2.6.0rc1 version
The preference dialog box is apparently the unloved child in Darktable as it still looks like the dialog box of an alpha version (long lists of unrelated preferences with no effort to make it more user friendly), not an organized dialog box like it should be in a 2.x version. Darktable is the only software with such impractical preferences dialog box, even softwares still in beta have more organized preference dialog box.
Preferences should at least be grouped by panels with title to make it easy to find the preference we look for. Look at any other software for reference, or any image related software to have a reference on how to group preferences (Geeqie, Pix, Shotwell, GIMP, Rapid Photo Dowloader, Rawtherapee, they are all lightyears ahead in term of preference GUI).