In the UMG editor, Add two widgets to a canvas panel. Select both of those new widgets, right click-> Wrap With vertical (or horizontal) box. It’ll create multiple instances of the same widget tree. These extra widgets have the same reference, so any change made to one changes all of them. You cannot delete them individually because of that as well.
If you have a widget that requires a unique name, the blueprint cannot compile in this state. Saving and restarting the editor doesn’t fix it.
This affects both 4.6 and 4.7