Come utilizzare un dock separato per ciascun monitor? [duplicare]

Sfortunatamente, OS X non supporta più dock contemporaneamente su più monitor.

In base a articolo di supporto di Apple :

When the Dock is configured to appear at the bottom of your screen, it's available on whichever screen you’re working on. Just move your pointer to the bottom of either display. When the Dock is configured for the left or right position, it appears on the leftmost or rightmost display edge.

Tip: If you don't see your dock because it's set to hidden or there's a full screen app on the display, move your pointer to the location of the Dock. If the Dock still doesn't appear, swipe your pointer towards the Dock again to unhide it.