This is pretty fundamental toward ease of use. The ability to copy and paste or save for future use any asset that has been altered. Also, and very important, the ability to select various assets as a group/layer in order to either copy/past or save them together. To this end, a selection pane (like powerpoint and many others) that lists all of the assets in the current scene and allows them to be selected/grouped and temporarily hidden for world building, would be very key to making world building much cleaner/easier.