Anyone know how to call SetModifiedFlag() from C# machine?
I can't find a way to do that directly but I think if you make any change to a machine parameter/attribute/position/whatever then Buzz would notice and set the song modified itself.
The only thing I found is BuzzGUI.Common.Settings.Setting.IsModified which is a property of the Setting class, so perhaps you could find an instance of Setting and set that property manually (if you're allowed) and Buzz would notice?
I don't think there's a way to prevent the addition of a track in the sequencer. I suspect the best you could do is automatically remove it after your machine has been created but I don't know if that's possible.
Sorry I can't help more.