I have DarnUI. You are saying go into those files and change them or are you saying Darn should be doing this?
I just went through it again and didn't see an option for compass marker.
You need to open those files and edit them yourself. I think you can set the markers on and off through the ingame menu, but the menu is really for experimenting with different HUD layouts since DarNUI can't save the settings. All permanent changes must be done through the XML files.
Just get into the XML, press ctrl+F, and type in <
_cshow_questtarget> (sorry, last post had a typo) to find the entry.
Do the same thing for map_config, but type <_show_qm>