Minimalist skin

This should do it:

foreach (var f in Rhino.RhinoApp.ToolbarFiles)
  f.Close(false);
Rhino.UI.ToolbarFileCollection.MruSidebarIsVisible = false;
Rhino.UI.ToolbarFileCollection.SidebarIsVisible = false;

I am not sure this is possible. Why do you need to do this?

Instead of hiding and/or changing appearance settings in OnMainFrameWindowCreated, try doing it in OnEndLoadPlugIn. Here, Rhino should be up-and-running, which isn’t the case when the the mainframe is created.

– Dale