Thanks guys, this advice was really useful and I managed to create new elements from scratch and then convert them into sub-props.
Whilst doing that, I noticed that CC already recognises the meshes for the lid (before I did anything) - it's called 'Cover' and 'Main' so I was wondering if it's possible to just convert what it already sees?
At the moment, when selecting those parts, it doesn't allow you to do anything with them, it doesn't select or highlight the parts or anything.
I'm trying to recognise what that icon is representing for 'Cover' and wondering if there's a way I can convert it in some way? - there doesn't appear to be a 'convert to sub-prop available' so I am guessing if there's another way, its through another method? grateful for your thoughts.
The original method explained in the thread works fine though, so I've got a way to separate it but just wondering if there's an even quicker way, seeing as it recognises it in some way, thanks.