Migrating Roofs and Skylights

If you prefer to display Single-plane Roofs (and any Skylights they contain) in ARCHICAD 20 as they were in ARCHICAD 14 and earlier - that is, their top surface only (Symbolic) - you can switch this as a Project Preference: go to Options > Project Preferences > Legacy. Under Legacy Options, choose “Use Symbolic Display in Floor Plan for Single-plane Roofs and their Skylights”, as your preferred display mode.