"You do not have sufficient permission to save the following content to disk. Any changes you make to this content will only apply during the current editor session.
/Game/Blueprints/AtomBP
/Game/Untitled
"
(these are the two blueprints I edited, the second one is a level blueprint)
You installed unreal as administrator. Now you are running it as normal user. Unreal cannot write to disk.
Run it (unreal) as administrator, should be safe, but not advised.
Turn of UAC, this will turn off most of windows security (which is not that good anyway). But better don’t do it if you ever go to unsafe pages on internet.