Revit plan views show overhead (eg stair parts, walkways)

IN floor plan view > VIEW PROPERTIES > turn on underlay for the level where the feature is set (say an intermediate landing or gantry)

In VIEW PROPS  set underlay orientation to RCP

Then use the underlay RCP outline to trace around in underlay line style (its a model line so not view specific) using pickline tool. Not sure whether needs locking to the feature to move with any changes.

Then switch back to plan and turn off the underlay. The model lines then display as symbolic to the feature in the floor plan.

Use for roof overhangs or anything overhead that is to display in plan view. Its a lot easier to do by this method than setting a PLAN REGION 

Thanks again to Alfredo Medina for highlighting this method.