Is there a way to access just the stem of the filename when using metadata? Something like {name|noext} or {name_stem}?
Usually done using a wildcard, with Ignore Extension turned on.
Are you in a situation where that won't work?
Yes. Mostly in cases when I want to use the Rename regex to create new folders and Ignore extension turned on. Using {name} as the new name will result in a doubled extension. As a workaround I use some jscript (return getNewNameData.newname_stem), which is usually easier than putting back together the capture groups.
So {name_stem} is not a must, but would be nice to have 
You may be able to use \0 in the regex to get the full name (without extension), depending on the details of what you're doing.
Yes, works! Brilliant! Thanks!
I don't want to steal this thread, but please allow me to step in here.
An old thread exists, titled
"standard-rename-how-to-get-the-filename-without-extension"
The {name|noext} was suggested there, but didn't work back then and so far has not been introduced.
Please correct me if I am wrong.
'Solutions' were always related to scripting and/or regex.
I had a number of occasions where I needed the filename without extension, checked the old site above.
Coincidentally I needed it again just now and stumbled over this recent thread.
Q: Could this {name|noext} not be reconsidered?
Thanks.
(I now made a preset)