Radio - put a stop marker in a playlist/queue

Sometimes I put tracks into the radio playlist and put together a couple of hours of tracks. I want to be able to say “end of queue” and not to go back to radio selecting more tracks after that queue has finished.

As much as I love the radio feature, it gives me six suggestions that make sense followed by four or five that don’t and when I come to the end of my queue I would rather that it looped and went back to the beginning.

Case in point Gotye is the track it is trying to match, after six similar tracks up comes Ibiza Dance tracks.

Also, is it possible to change on the fly the control track that radio is trying to find “similar” music for. e.g. a suggestion comes up in radio that I like and I want to be able to “change the similar to” to focus on this new track.

I know that we have FOCUS on the track playing, it would be good to have that in queues?

Thanks in advance