Pie Menu Editor 1.18.7

Yes, you can store functions in Stack Key slots. And call them from the button using this code in Command tab (video):

open_menu("Stack Key", event_mods(E))

Where event_mods(E) function returns key modifier combination (e.g. Ctrl+Shift, Alt+OSKey, None).
And open_menu() function calls Stack Key’s slot by its name.

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