test.js

// cancel the click handler of the "Footnote" menu item
TXTextControl.addEventListener("contextMenuOpening", (e) => {

	// check if e.items contains an entry where property text == "Insert"
	const index = e.items.findIndex((i) => i.text === "Insert");

	// check if e.items[index].items contains an entry where property text == "Footnote"
	const index2 = e.items[index].items.findIndex((i) => i.text === "Footnote");

	// if so, cancel the click handler
	e.items[index].items[index2].clickHandler = function(e) { 
		e.cancel = true; alert("Footnote is disabled"); 
	}
	
})