JabRef 5.2 it is possible to use custom themes. In
Preferences > Appearance > Visual theme the themes in general can be changed. Themes are just CSS files defining the look of the UI.
Light Theme: The default theme is the light theme (
Dark Theme: There is an alternative dark theme (
Dark.css) which is based on
Base.css and just overwrites the colors.
Custom Theme: In
Preferences > Appearance > Visual theme > Custom theme there can be set a custom theme by simply selecting a custom CSS (based on
Dark.css), for instance:
Custom Theme (based on the Dark Theme)