Using Dex, how Create multiple desktops on UI 8, Android 16, ZF7 (opens in new tab)

As title says I'm trying to add multiple desktops supposedly up to four using Samsung Dex on zf7 connected to external monitor. Instructions via a search on Google suggest in 8.5 or 8.0 UIs there is a plus symbol and I cannot find this. Anybody have suggestions, insights or is this unavailable...