After a lot of googling, I had to eat my pride and ask you guys ;)
Reorganizing the SiteTree menu backend in SilverStripe is easy with drag ann drop, but how do I get this reorganizing to be visible on the frontend, i.e. the menu. How can I reorganize the backend with drag and drop, and get that exact same structure frontend?
From what I've googled, I see that you had an option in SilverStripe 2.4 to do this. I can't find it any options for this in 3.0 backend, so I thought maybe I had to set a config variable to activate it. But I can't find anything there either.
Hopefully this is suuuuper easy, and most of you will facepalm as a direct cause of my question.
It really should just be dragging the pages to the desired order. Remember to save and publish the page you moved.
If you refresh the admin panel, are the pages still in the order that you dragged them to?
EDIT: After moving a page in the tree, it should say "modified" next to it. Also the messaging should display sitetree reorganised.