SSIDs on different radios?

I have 2 APs (A and B) broadcasting 2 SSIDs (x and y) on 5 Ghz.

On AP B, SSID y is also broadcast on 2 GHz but does not need to be broadcast on 5 GHz.

I would like to change the above so that SSID y does not broadcast on 5 GHz on AP B.

On AP A, I would like to also broadcast SSID y but only on 2 GHz.

I cannot see how to do this using the new interface.

Any suggestions?