I'm sorry, but the Design Options setup is atrocious. It is unintuitive, and I can't even follow what the intructions are trying to say in it's convoluted explanation.
Why can't objects simply have a "parameter" of which they are to be on. That option then can be selected as on or off in visibilty graphics. End of story!
Jeez
Atrocious, indeed. Especially when Spaces cannot belong to a Design Option. And that Systems cannot "cross" Design Options, meaning that if branch circuiting is different between two Design Options (but still fed from the host panel either way), the entire Systems must be recreated in BOTH options.
Anyway, you *can* create a Project Parameter to act as a "Design Option" and apply it to all model elements. Then create a View Filter to show the plans properly, and Filters to show Schedule appropriately. However, there are going to be downsides to this, one such being with clash detection. Design Options also keep the elements on separate Options from interfering and interacting with each other, whereas the parameter method, not so much.
Good idea with the parameter to control visiblity.
I did not know that about spaces and was curious how it worked with systems. That just gives me another reason not to bother using systems. Too much effort involved, high chance it can be unreliable, can be impossible without using undesired duct ductwork/fittings. Sad but true.
Thanks CADastrope