I have searched around, but came up short. I know something needs to be done with the . (dot) to keep it from recognizing all characters, but the brackets, slashes and quotes are not giving me the result.
I have a large collection of live recordings and realized it is a little tough to look at with the current tag:
Create an action of the type "Replace with regular expression".
Enter as Search string:
^(\d\d\d\d).(\d\d).(\d\d),(.*)
Enter as Replace string:
$1-$2-$3,$4
Works if you have the date at the beginning of the string and a comma behind it.