More formatting controls (headers, tables etc)
I recently discovered that Hashnode supports much more of Markdown than what the editor suggests.
It's 100% possible to use "###" for headers, and do tables etc, and it all looks great. The editor toolbar doesn't really give the impression that all of this is possible though.
It'd be great to add some more options to the toolbar, like setting header size, adding tables etc. If that's not in line with your plans (keeping things simple?) then perhaps change the tooltip from "Markdown shortcuts" to explain the fact that you can use all valid Markdown a bit more clearly?