is it me or do I look in the wrong way…
how can a user add a blog post.
and can I restrict that user to only add post in the blog page folder
You can’t restrict a user to ONLY create blog posts. You can create a user and restrict their access to only have admin.login and admin.pages permissions, rather than all (admin.super).
Can you add this toe the wish list?
It’s something that will be coming in the Pro version of the admin.
When can we aspect the Pro version 
We’re working on it now… no eta as yet.