In Rhino 5 I used to be able to import displaymodes using the OptionsImport command.
RhinoApp.RunScript("-_OptionsImport file.ini _AdvDisplay=Yes _Enter", false);
This no longer works in Rhino 6. .Ini files exported from Rhino 6 throw the error “The selected file is not a valid options file” when I try to import them back into Rhino 6. (.ini example here.)
The import button on the Rhino Options > Display Modes page works, but I need to be able to do this programatically. Is there a Rhinoscript/Rhinocommon solution for this in R6?