Both of those were typed by hand without needing to paste or switch to Regular Expressions and back again.
Are there any other valid places where you would want want to type a colon but can't currently?
Mainly because that's just what the syntax is, but also because backslashes cause problems in general, as they are an escape character in a lot of contexts/languages. (It's unfortunate Windows uses them as a path separator, but we can't do anything about that.)
I think I see it. If I literally type {scp:, it works perfectly. In my case I was Editing an existing New name: field.
If you type a : while editing the New name field, it isnt accepted. It has to be after {scp and at the end of the line. In my case I was trying to convert {parent} - * to {scp:TitleMatch/name} - * without first deleting the entire line.