Does anyone know if there is a JS editor that acts similar to how notion works? I've seen a similar pattern with readme.io, and would love to be able to use it for internal tools.
The closest I've found otherwise is ContendBuilder.js:
http://www.innovastudio.com/content-builder.aspx
SirTrevor is similar, but without drag+drop:
http://madebymany.github.io/sir-trevor-js/example.html
For us, it was built using two linked jQuery Sortable lists (the sidebar, and the actual content). It's easier than it sounds, especially with Angular :)
Notion is actually really well constructed (as somebody who's been in the space building tools kinda like it for a while, it's quite impressive). But I agree, the space needs an open source notion...