Context menu mimic behavior of window’s context menu, and doesn’t support such feature.
But it can be added with relative small code modification
The menu has two inner methods:
_onItemOut
_onItemOver
both located in dhtmlxMenu.js, lines 1270-1290. You can add custom code
which starts 3sec timer in _onItemOut and drop it in _onItemOver. In such
case timer will fire in 3sec after mouse was moved out from menu.