@Fuzzio, thanks anyway.
Thanks a lot.
That's what I was looking for.
I have to say that it's not the first I struggle with that kind of stuff in the Silverstripe documentation.
How did you know that the content of TreeDropdownField field can be displayed as URL or as Relative path?
What are the other options?
Where do you find that kind of info?
I seem to only get it from reading posts on the forum of users who have already used it before (e.g. that's how I found out about $Locale.Nice)
(Probably very weird question I know)