User role - Create post only

Hello kind Perch community. I'm on my very first days of my first Perch project and really excited already.

No more introductions however, there you are my inquiry: We need to build a space for external collaborators to add blog posts. I created a new role and grant access to create blog posts. However when I log in with a test collaborator account there is no option to add a post. If I add to the collaborator the permission "Access the blog", then I do get an "Add Post" button but also the ability to edit the already existing posts(Not created by this collaborator). Is there a way to allow a user only write new blog posts and nothing else?

Many thanks in advance for your help.