99% of all searches I make are just plain text and I don't need the ability to save them. However, when a regular expression is used it would be very handy to save it so it could be retrieved for a future search.
The main reason is that getting regular expressons right can take some time, especially because a programmer using mutliple language is often faced with a variety of syntaxes. They are hard to remember. I find I have to re-learn the syntax for Rapid (and for Microsoft Expression Web) every time I use a regex.
I recommend saving the search queries in %appdata% with a file extension such as .srx (for Search RegeX) or .bsq (Blumentals Search Query). FrontPage and Expression Web use .fpq (FrontPage Query).
On a related subject, a matter I think was probably closed 10 years ago, I do not think Rapid needs a RegEx wizard. I use RegexBuddy. I'd rather see Blumentals' resources directed at IDE and editor improvements.