As blogger I want to be able to start write posts but not publish, so that I only publish finished content.

[clarete]

This is possible with two things:

1. add the #+DRAFT: t file tag in your posts
2. add the #'blorg-input-filter-drafts to your publish.el

(blorg-route
 :name "posts"
 :input-pattern "posts/*.org"
 :input-filter #'blorg-input-filter-drafts
 :template "post.html"
 :output "blog/{{ slug }}.html"
 :url "/blog/{{ slug }}.html")

Org-Mode file, let's say "posts/a-nice-but.org"

#+TITLE: A nice but incomplete post
#+DRAFT: t

something we'll never see because it's going to be filtered