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

Archive Python API
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I would like to move two functions in the Grouped sub menu, but the menu isn’t defined in spacer_sequencer.py and the name of the menu isn’t listed here: https://en.wikibooks.org/wiki/Blender_3D:_Noob_to_Pro/Advanced_Tutorials/Python_Scripting/Object,_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")

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