I recently made a very similar tool but focused on making small React apps instead of presentations.
A basic starter html file with an example app: https://glider-app.netlify.app/glider.html
Docs: https://glider-app.netlify.app/docs.html
The docs aren't very polished yet but it's quite usable!
It bundles a JSX transpiler, a code editor, and supports saving to a file or localstorage. It supports "ejecting" to separate the shell (handling saving files, transpiling, editing, etc) from the JSX and the JSON data.
I also threw together an iOS app in which you can save these mini apps, allowing for longer term saving of data and code edits without relying on localstorage alone, making the save/refresh loop seamless. It includes a sandbox, preventing any saved mini apps from making network calls, but allows the user to enable network usage on a per-app basis. I'd like to include more QoL features like a native editor, but haven't prioritized that yet.
I checked it out and it looks cool. It's a much more general platform than Bento. If you can make it do presentations, I'm sure the actual quality of the output would be better than Bento as it's React as compared to reveal.js.