Hi @c.houben!
In the latest release of the Universal GUI, we’ve made darkmode a (couple of) shade(s) darker, which should fix part of your issue! Be sure to update your Universal version to the latest version, and you're all set!
Keep in mind though, that dark colors in dark mode will make it hard to distinguish the colorized elements. If I take a lighter color, elected/hovered rows are way better to see:

Compare it with driving through the night: if we want to see something, we use lights and bright colors to stand out. Dark colors will fade to hues of black.
Kind regards,
Bart