Append function to VSE > Header > Menu > Select > Grouped > Sub menu?

I would like to move two functions in the Grouped sub menu, but the menu isn’t defined in and the name of the menu isn’t listed here:,_Action,_Settings#Undocumented_Blender

So how do I append functions to that menu?

This (guess) doesn’t work:
bpy.types.SEQUENCER_MT_select_grouped.append("sequencer.select_all_mute_strips", text ="Muted/Hidden")