Okay if the feature is primitive then regardless of booleans you ought be able to extract a new and separate copy. however it is something like a hole a pocket or even a pad then it lives on another solid by its very nature and can only be pasted in that context. That also explains to some extent why most sketches would appear to work.
However what you can always do is to extract solids, sheets, points or curves from one part to another. Probably the easiest way is to wave link them and if you don't wish them to remain associative then break the links or remove parameters.
In a specific example we might be more instructive but this gives you the broad sense of it.
Best Regards
Hudson
www.jamb.com.au
Nil Desperandum illegitimi non carborundum