If you right-click in the browser text editor, it says "Redo (CTRL+Y)".
I'm not sure about other environments, but in mine, CTRL+Y pops up the emergency debugger. You can't redo any text changes using the keyboard shortcut in the browser.
This can't be used after deployment as this particular context menu seems to be specific to code editors (or maybe just the browser?), and the browser gets stripped out. The usual context menus don't show these shortcuts to the user although they work fine.