The curves you use the generate surfaces and solids in MoI, remain... Just after you create and object like this, they will actually remain "selected".. You can either rename/stylize them to hide and keep, or delete right away..

Actually, MoI has a history mechanism.. Just after you generate your network, turn on control points for one of those generating curves, and adjust it a bit... You'll see the command calculation begin again, and the surface/solid will update!!!

FYI