Maybe try dollar quoted string constants as explained here: https://docs.snowflake.com/en/sql-reference/data-types-text#label-dollar-quoted-string-constants

This expression worked when testing against your string on https://regexr.com/

(\w\s?)+(?=(\(\w+\))?([T].{1,3}[N]\:))

According to the documentation you'd use

$$(\w\s?)+(?=(\(\w+\))?([T].{1,3}[N]\:))$$

Seems strange to exclude parts of regex.