I find me using this function extensively. But it could be much easier, if we could define the second key using a simple comma (or commas), followed by the other keys,
instead choosing that option from the small dropdown menu, especially, when defining some triple key combinations.
So, what i suggest is, that we could enter the initial key (like Alt-D), enter a comma then, & can go on typing the second key, & so on. I suppose, that no one is going
to use commas as a function key, so that character would be available as a control key, to form a multi key sequence.