Was using Reveal.js which worked well because it can use any HTML or any plugin.

Bento works with a predefined schema, so you cant use any HTML library (Such as Mermaid.js) if you need it in your presentation.

But then again, often you dont need it.

Just created a presentation with Bento... I do think Reveal.js gives you more raw power. But I like bentos single html page design, and you can easily edit it manually. You cant do that with Reveal.js

Yup, I'm trying to see if we can add arbitrary JS. I think it may be possible, but would take a bit longer to test out different approaches. However I guess the main target audience for this is coders that interact with non-coders when doing presentations, and I think currently this approach is sufficient.