There is no option I am aware of to keep the editor as a single window application. You end up with ,multiple windows open on the desktop which quickly gets confusing if you have more than one instance of UE running with multiple projects open.
And the first thing I do when opening a project is to drag all the tabbed asset editors to the main application window. Huge time waste. No other application I’ve used on any platform works like this.
If you go to Engine Preferences / Settings, under “Appearances” you can chose to open new assets in the “Main Window” - that will effectively keep almost everything opened in your main application window, as you asked for.
I know how annoying that was, until I learned about this option.
