You can do this by creating a second 'Board' in the project and use this for the simulation including your cable. Use hierarchy so that the real board schematic can be inserted as a block in this 'simulation' board. Then it will share the same schematic and changes in one 'Board' will be reflected in the other 'Board' without needing to make changes in each instance.
In the second question set 'Forward to PCB' = False for your parasitic discrete component ans it won't go to layout. But if you use the two board solution it shouldn't matter anyway.