While you should be okay using the + sign in your system name, I
would recommend against it from a best practices point of view. For
SEO purposes, I would stick to alphanumeric characters and dashes
(not even use underscores).
Hope this helps.
Thanks for the response, Kat! I appreciate the point about SEO.
This is a very unusual and specific situation where I need to be
able to match on a non-standard character from a folder name, so
good to know that "+" is allowable in Cascade. I assume a period is
allowable as well?