Late to the party, but there's a "canvas mode" in Obsidian where you can sort of group notes together and drag them around. Other than that, it's also got a graph view, so provided you tag and link notes properly, it will show you related notes in the graph.

It is based on markdown files and you can link them by writing "[[my new note]]". It also supports tags etc, all text-based.

What is the purpose of the "dragging notes" flow you mention? I am sure it can be done in the text-first way that Obsidian uses.