How to add a second chamber in the same box?

Hey all. 

I'm designing a vented box that requires a closed chamber in the top to add a horn/compressed driver. 

Under the box structure (vented), I can see the Chamber #1, which has my 10" mid/bass, but I'd like to add a second closed chamber in the top to allocate the compressed driver/horn, separating the midbass from the compression driver. 

Is there a way to have multiple chambers in the same box? 

Yes you can have multiple enclosure in the one box. You should open the Structure window, then press on the item that represent full box and then by keeping hold move it to other chamber of another box.