You might want to consider a tool like Trello to organize story ideas and drafts. I say this as someone who has lots of ideas for stories, for different publications. I set upa Trello board that's almost like a Kanban board. Lists for Ideas, stories in Draft, Submitted, and Published. Also have a list for stale ideas. I have labels for which publication I'm writing it for.

I try to use tools that are suited for the task. I don't see Medium as the place to dump every thought. Just a suggestion.

I sometimes do write in Google docs because I can save versions and add notes and comments. And I can ask a friend to make suggestions in a shared doc.