Unfortunately you can’t put a door on the top. You can add hinges to the top panel so that the production documents are correct but the top will not open like a door in the Polyboard 3D mode.
The slack around the top can be adjusted as if it was a door using the “links” section of the Properties menu:
To get a visual with the top open you have to export the 3D DXF file to another CAD program like SketchUp.
i was trying to make a bench, for my dad birday, with a door on the top, but i have no idea how to make a cabinet with the front panel and a door on top.