In Windows, 'auto hide' is an optional setting. The Deskbar retracts, if the 'auto hide' option is set. If retracted, a mouseover makes it visible and a mouseout retracts it once more.
If this were available in Haiku, no matter where you place the Deskbar, bottom, right, left or top, the functionality applies.
Another setting is 'always on top'. When the Deskbar is visible, any window sharing the same space is occluded, if 'always on top' is selected, otherwise; the Deskbar is occluded by any window sharing the same space.
The two options are independent of each other.