I joined Steemit since July 2017
The very first thing that I looked for it the "Draft" button, and I couldn't find it. As most of the time, I tend to work on multiple ideas/posts over a long period, I'm sure other users are looking for this option too.
Workaround
So for now, I just copy over my drafts to my local editor that support Markdown - Atom.
So...
Dear Steemit,
Please enable support for drafts. I'm sure the whole community will appreciate this function most. :)