How to use Unreal 4 to pack a program twice?

I want to use UE4 make a development tool.
For example, I have a UE4 program, which includes a level and several buttons that can dynamically operate the level. This program is packaged and released by UE4. As a separate program. After opening the program, the user can click the button to add some pre-made 3D models or some attribute changes to the level. Then the player can package the levels in the program to generate a new independent program. How can I do it?
(Or, you can think that I made a new game engine program using Unreal 4 engine, and the new game engine can package the program)


It is best to package the entire scene directly in real time.