I’m trying to find a way in which (logged-in) users (without any knowledge of GetGrav) can add blogposts.
I’ve installed “Editable With SimpleMDE” which allows editing existing pages but I can’t find how to add directoeries/pages.
I’ve looked at “add-page-by-form” but I find the docs daunting and I worry about the lack of a default form/setup.
I’ve tried “edit-this-page” but this throws a user immediately in the admin panel, which is unsuitable for these users.
That’s not trivial, you need a form that can submit content, then a plugin that will automatically do something with that blog post. Either simply email you the content and you can create the page manually, or a custom plugin that takes that form submission and creates an unpublished Grav-page in a submissions folder or something.
You could use parts of the admin plugin to achieve this but you have to be careful to ensure it’s safe and not exposing your site to potential security issues.
The two plugins you mention, although not intended as such, are quite complementary and could make for a nice frontend blogging solution. The docs may be daunting at first but I suggest you start experimenting using the blog post example form provided.
The missing part is in some user interface elements and, I think, these are hard to make generic. With that I mean that these elements must get positioned and styled (and work!) in whatever theme is used.