Similarly to triggers that have comments and to item (planed it ZBXNEXT-511) and maintenances that have descriptions, Regexps should have descriptions too.

Why?
Name of regular expression is used elsewhere, so it is best to do a short one. It is not always possible in a short name to put a precise meaning.
And when the regular expressions is a lot, then you can get lost that is used for what purpose. In this situation, the description should greatly help.

This description can be displayed when view a list of all expression - there is enough free space.

It would also be useful when deleting the expression to check into how many items and triggers it is used. For example, as is done recently to value mapping. Is at your decision.