Select your already constrained parts or assemblies by creating a window with your mouse or holding down Ctrl and clicking the part with your right mouse button.
Copy with Ctrl+C. Then paste wtih Ctrl+V to your desired location.
It’s copying constrained selected parts/assemblies to a new location.
Then constrain the already pre-constrained parts/assemblies to where they need to be.
Also it works between different model windows.
It’s really great time saver.