We have considered removing regular expression support from keywords. We originally weren’t even sure if we should have implemented it and it causes issues for folks that do not write efficient and compact regular expressions. Add in the fact that Rhino does not support some regular expression features, and it makes for a difficult to support feature.
Keywords are really meant to be, well, keywords, not keyphrases. As such, the panel was designed for keywords - a word. We already had to hack at the panel to support characters that it was never meant to support which has added layers of complexity. A possibility may end up being rejecting anything that is more than one word in the future and bringing this feature back to its original intent.