This is not something we support currently. Before, the simulation would just not do anything. Now there is an error message. In theory, a limited version of that could be supported eventually but it does not have high priority currently. The tricky aspect of supporting this is that each simulation has a cache, can be baked etc and we need a persistent identify for those. That's not possible if simulations can be added and removed dynamically all the time. Pull Request: https://projects.blender.org/blender/blender/pulls/139479