I realise this has probably been covered many many times but it's proving to be difficult to nail down an answer in this case.
I have an established group: a background shot with a semi transparent polygon to give it gravitas. Done. Happy. Brilliant.
However, now I have another rectangle that I'd like to add to this group - let's call it "BG". I've tried ctrl+click and drag onto the group - no luck. Select the group and the new element and use CTRL+G - nada.
Am I missing something here? please?