All Roofs, including dome and vaulted Roofs, will be turned into a set of Single-plane Roofs in ARCHICAD 20. In outward appearance, your Roofs will not change.
By default, all newly placed Roofs and Skylights in ARCHICAD 20 will be displayed on the Floor Plan showing all visible contours, as if projected from a 3D view (True 3D Projection).
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.
If you migrate an older-version project containing Skylights placed with the Skylight tool, they will be automatically converted into ARCHICAD 20 Skylights, with all their parameters preserved, and capable of all Skylight functionality that is available in ARCHICAD 20. However, their display on the Floor Plan will, by default, remain “symbolic,” as it was in the earlier project version. In outward appearance, your Skylights will not change, and their Floor Plan display parameters will be retained, although these are not available for Skylights in ARCHICAD 20.
Skylights that were placed using the Object tool will remain objects, and will lack the full functionality of ARCHICAD 20 Skylights.