SUMMARY
This is something Windows Explorer does and is actually quite nice. If the user wants to move say their "Documents" or "Videos" folder to a different location or even drive, they can right click the folder, go to folder properties and set a new location for that folder. It will make a new folder on the new location, ask the user if the contents of the old location should be moved over there too, and from that point on the "Documents" folder will be in the new location.

To do the same on Linux right now you have to manually edit a config file, specifically "$HOME/.config/user-dirs.dirs", which is bad UX imo. Then people will say "just mount your /home on a different drive" but maybe you want to move only the Videos folder. And I'd say mounting /home somewhere else than going with your distros default is quite an advanced task, not suitable for the average user. It would be nice if Dolphin allowed changing those folder locations via the folder properties window.

When typing this bug I found https://bugs.kde.org/show_bug.cgi?id=428112 through which I realized it was already possible to move these locations, but I find the systemsettings quite an intuitive place. If I hadn't found that bug, I wouldn't have known it was possible to change those locations via a GUI at all. I'd say Dolphin should have this functionality also, even just to cater to old Windows users, _alongside_ systemsettings having the option.