What you have to remember about the 2D plan view is it is a symbolic view of the model and not a true 3D top view.
So unlike the 3D view or sections and elevations you are not seeing elements in their true space but simply 2D line representations of them.
They do have a default hierarchy in plan - slabs below walls, then beams roofs, lines, text - but don't quote me on that order.
Display order can be used to alter their hierarchy.
Also there is a setting (Options > Project Preferences maybe - I don't have Archicad running at the moment) where you can set the line type for elements above and below.
Them tell the element to display on the home storey and one storey above or below - and the line type will automatically change depending what storey you are on.
Also you can set the Floor Plan Display option of the element and set the uncut and overhead line types in the element.
Then depending on the position of the element above or below the Floor Plan Cutting Plane the line type will alter.
Quite a few options but sometimes it is easier / better / necessary to 'fake' it with 2D lines.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11