Change active window ??

When im using in traktor pro the shift+ back i can switch decks screen to browser very simple. Is there anyway to do so with rekordbox ?

In linux and windows alt+tab (or alt shift tab for reverse action) switches between opened windows. Guess there's something similar if not the same in mac.

If you mean the the music browser in rekordbox, space is the default key which you can change in keyboard assignments.

I mean which button in my sx2 do so ???

If the sx2 manual doesn't mention a button for it (for serato at least) then chances are there is no dedicated button for it on the controller hence, no default mapping.

You can try to map it on RB though and see if it works but if there is no dedicated button you'll have to sacrifice one on the controller for this.

In RB go to "preferences" "keyboard", expand "Browser" and is is the last option (which defaults to "space" key, ofc)

Is the rotary button to select tracks also a push button? if so this would be a very good option :) (again, assuming it is possible to map.