From Xojo Documentation
Design Property (as Integer)
The window type. Set the desired Frame type in the Inspector.
Frame is set to one of the following values:
|1||Movable Modal window|
|2||Modal Dialog box|
|7||Global floating window|
|8||Sheet window (macOS only, displays as movable modal dialog on Windows/Linux)|
|9||Metal window (macOS only, although rarely used and deprecated by Apple)|
|10||Drawer window (No longer supported).|
|11||Modeless Dialog box (displayed as a Document window for OSs that do not have this concept)|
The various frame types are covered in the User Guide.