@leocg There is a keyboard shortcut Ctrl+Space that opens a window to look through tabs. No issues there. Why not add a function there to enter a URL in the search bar?
Ok, I found the solution. In a new tab (I have speed dials there) with the right mouse button you can call the popup menu and select Edit theme. There you can switch on the dark mode. This worked for me. I hope that it will be useful to someone else.