Add a button to the object add pannel's grease pencil menu

How can I can i add a new button to the Shift + A object add panel under the grease pencil menu? I would like to customize it. For the mesh pannel it is easy with defining a operator subclass and:

def menu_func(self, context):


But there isn’t a VIEW3D_MT_gpencil_add.

Also how could I remove an existing button or the entire Grease Pencil menu? (In case there is no way i would recreate this submenu then. I guess is the only way to customize it)