BBEdit 13 has been released with some really nice improvements around find. I particularly like that when editing the search string in the Find window, it now highlights the matches in your document. Although, unfortunately, it doesn’t yet preview the result of a replace.
The headlining feature is called the “Pattern Playground” window (created via “File” -> “New” -> “Pattern Playground”). It’s a way to make composing Grep patterns easier by showing matches and capture groups live.