Hello @Mary-And-Sean0 @Patricio2
I'm not sure why this conversation is showing as being answered so to answer your question for adding an extra room to your existing listing Mary and Sean without of course losing your great reviews follow these steps:
==>Host mode
==>Listings
==>Your space Edit
==>Add a room or space Edit
==>Select bedroom and fill in the details, add photos etc
==>Save
I have opted in for the early new release so I'm hoping these steps are not too dissimilar for you that haven't yet taken the plunge😉
P.S. You should be aware that some of us, the order of the bedrooms is reversed but this does not stop us from adding an extra bedroom
All the best
Joëlle