Create a custom keyboard shortcut in stackedit.io?

As a user of the stackedit.io web app, can I create custom keyboard shortcuts for my own commonly used tasks?

It seems like the Settings YAML would provide for that option, and there is a reference to the Mousetrap documentation, but I’m not sure how to tie these two things together. Does one simply start typing JavaScript code into the YAML settings editor, or … ?

I searched high and low for a simple example of a custom keyboard shortcut, and found a reference to someone trying to do something complex with JavaScript, but I’m lacking the critical piece of information as to where one would put all of that JavaScript code, or whether this is something that can even be done in the stackedit.io interface.

I couldn’t tag this question stackedit because I don’t have enough reputation to do so.