string TooltipHeading {get; set;}

// programmatically activates the Edit Annotation tool by invoking the corresponding
// plugin. The tool must be enabled for the operation to succeed.
{
  var plugin = FrameworkApplication.GetPlugInWrapper("esri_editing_EditVerticesText");
  if (plugin.Enabled)
    ((ICommand)plugin).Execute(null);
}

{
  //Pass in the id of your button. Or pass in any Pro button ID.
  IPlugInWrapper wrapper = FrameworkApplication.GetPlugInWrapper(proButtonID);
  var buttonTooltipHeading = wrapper.TooltipHeading;
}