What special operators are supported in Notepad++ UDLs other than ((EOL))?

When writing a User Defined Language in Notepad++, entering ((EOL)) as a closing character will end a delimiter group after any end of line character combination. (rn, n, or r).

Open: ##, Close: ((EOL))

Result

The Notepad++ User Manual refers to (( )) as a special operator, but doesn’t specify any other strings it will transform. Most special characters like wildcard * or the previously mentioned new-line n get treated as literals, so having access to other special characters would be useful.

Are there any special operators other than ((EOL)) that get transformed in a Notepad++ UDL?