Comment 1 for bug 1400377

This can be achieved by setting window snapping on chosen trigger eges to top half and bottom half.

Per screen settings are not supported by unity to the best of my knowledge, so unfortunately this is not possible right now. If you manage to find any way this can be done, please inform us and we'll add the feature after studying how it can be done.

Meanwhile, if you have both a portrait screen and a landscape screen, and need snapping for top/bottom and left/right, a workaround is to set window snapping triggers on all four edges to fill the respective halves ( top edge for top half and so on) and use a corner for maximize.

Unity project may want to look at this feature-request, I am marking as affects unity and closing for unity tweak tool.