I'm finding this frustrating. It appears that you must structure your components the way you finally decide you want them from the start.
For example I have a plane, sketch on that plan, 3 components related to the sketch and joints between them. Then I decided I want them all in a subassembly. I created the subassembly (component) and activated it. But when I try to move these previously created items, it won't do it. If I try to move any one of them, I get.
Detect some position features may result downstream features fail after restructure.
It says "may result" but it doesn't tell you what the failures might be. Since it won't do it, I can't find out.
Knowing there are some relationships between the items I wish to move I tried selecting ALL of them and moving into the new component. In this case there is no error message, it simply doesn't do anything.
So apparently the only way is to delete all the things you want to move, create the component you want them in and recreate them all. That's not good for a "design" tool.
I think this is unfortunate because this is something that almost always happens in the design process. I'm a software guy and in that case, I can restructure code as I please. Sure it might cause some problems but they can usually be fixed.