Is it possible yet in elements for end users at a website to add a new item?
If you mean “without Elements,” the answer is no.
If you mean “within Elements” right-click in the correct posts folder of your CMS and choose New Markdown file, fill out the YAML frontmatter dialog, and then type directly into the file.
Thank you. I willgive it a try….
The answer would be “not yet” 
It’s planned, but no-one knows when it will be featured.
Out of interest is it only Elements that requires references in the .md files to resources be all lower case or is this a general requirement of .md?
Well.. it is.
Ben mentions it. .. “ use Github”.
Bascially you maintain the folder on the site where your .md files reside with Github.
I have posted another question for people to share their knowledge who have done so. But to no avail.
I have stumbled over Obsidian, another software… Which seems suited for a task like that.
Long story short, nothing supported, easy, outof the Box yet. Technically, any program that can handle a folder of text files, has access privileges could be used.