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.