Something cool I’ve done with reveal.js slides: it’s just a web page, so why not embed an iframe? Instead of putting a slide that says “Now for a live demo!” and switching over to an editor, why not just embed an interactive editor?
For example, here’s a slide from a presentation where I was showing off some fun features we had built into Sorbet’s[1] LSP editor support:
https://sorbet.run/talks/RubyConf2019/#/18
The slide has the Sorbet web playground embedded as an iframe, so the demo file persists for anyone who wants to browse the slides later. You can play around with the same example I used on the day of the presentation.[2]