You can have easily fast access to 32 slots.

You can set a cross bar that appears doing Hold R2 then L2 and Hold L2 then R2
By default this option is not active.

@ Donjon : Just for information PS4 does have a lot more than 4 cross bars. 8 cross bars for starters but we can set more and even horizontal/vertical hotbars. I think we have same number as for PC