Google-docs – How to customize the toolbar in Google Docs

Is it still impossible to customize the toolbar with extra buttons? Specifically, I'd like to add the strikethrough one (especially with how horrendous the keystroke for it is), but a general solution would be better.

I know there used to be at least one script for this, but the one I've found is clearly outdated (Ive looked at the source code and there's no way it'd work with GDocs' current layout).

I also know that I can create scripts to add extra menus, but that is not what I'm looking for.

I am open to any solution that allows me to add a button to the toolbar, even if it's a lead on how to write a greasemonkey script for that.