OK, I’m quotng the relevant parts from the documentation.
Item scanning: The next two actions allow you to scan the name or text of a document and use the results when found. …
- Scan Name: Scans the name of the file.
…
The following four parameters are used with the Scan Name and Scan Text actions. …
- Regular Expression: Items in parentheses are captured; items outside parentheses are ignored. You can specify multiple captures in an expression. Using the captured text in subsequent actions is specified by using backslash,
\, and the number of the capture, starting at1. Note we use Apple’s NSRegularExpression which supports the ICU regular expression syntax.
So you have to use a regular expression, because it is not possible otherwise to refer to parts of the match.
The expression itself should look like this
(\d{4})(\d\d)(\d\d)(?:_?\d{4})(-.*)
and the replacement like this
\1_\2_\3\4
Explanation: \d is RegEx’ish for [0-9], think of “digits”. So we’re first capturing 4, 2, and another 2 digits in the capturing groups (delimited by parenthesis) 1, 2 and 3. Then comes a non-capturing group (?:...). It looks for an optional (?) underscore, followed by four digits (\d{4}). The last capturing group is (-.*), i.e. the “-Name” part in your example. This group is # 4, since non-capturing groups are not counted.
In the replacement part, you simply string together the capturing groups 1 through 4 with the underscores you want.
Since the rule only matches the file names you described, it should do what you want. Please test first with a copies! And adjust the rule accordingly if the part after the date is not four digits…