As I’ve started using KDE (alright- the KDE Software Compilation), one thing I’ve run into is that all the dialogs seem to default to certain folders. I ascribe to David Allen’s Getting Things Done and have tried to create a desktop environment that reinforces those habits. So I don’t use the ‘Documents’ folder. As it turns out if I had just deleted the folder the Documents path would have reverted to the home folder (supposedly).
But the better way is to adjust the paths the system looks for. You can find them under System Settings > About Me > Paths. That cleared up some of my problems. Say what you want about having too many options- it’s nice that there’s a nice UI to change those options.