The way to do this would be to create all the nodes at the beginning of the simulation, and then programmatically (by writing C code) turn on/off transmissions/receptions at the MAC Layer of the nodes.
We consider turning on/off transmission/reception as the equivalent of removing a node, from a networking perspective.
Useful articles:
what-are-some-best-practices-for-writing-my-own-code-in-netsim-