> With increasingly complex apps being built that often rely on memorizing shortcuts, what alternatives exist beyond good design?

I think it's key to make the shortcuts discoverable inline. Maybe by default, maybe with a modifier pressed, every button and menu item should show the shortcut for it.

Also take a look at the experience in Spacemacs, where you compose multiple keys for a shortcut and if you pause you get a pop-up showing possibilities (eg press , to get major mode specific, then pause to see options, press x for text, then pause to see all the options for the next letter. Then when you know it you just quickly hit ,xi) (I vaguely remember someone else wrote this and Spacemacs popularized it, but I can't find the name)