I use regular expressions quite frequently (and I was the one implemented this feature in LabVIEW), and I rarely write regular expressions which use more than the features mentioned in the documentation. Once you know how to use character classes ("[a-z]"), alternates ("cat|dog"), and repetition ("(foo)*", as well as + and {...}) you can already handle most use cases.
I realize there are many more things you can do with this syntax, and some people like to use those other features more often than others, but our goal is to keep the documentation as understandable as possible while covering the most important parts for the major use cases. I don't want to try to include comprehensive documentation on the entire syntax available.
If there are specific pieces of syntax which you feel are very important and are not covered then feel free to make a case for adding that, but try to keep in mind the principles I just described.
