Change group ID on files?
When editing an existing user, if the user's Primary Group is
changed then files owned by that group will remain owned by the old GID.
This option can be used to update the ownership on files to the new GID
by searching either the user's home directory (Home Dir), or the entire
filesystem (All Files). The All Files option may take a long time,
especially if you have many large or NFS mounted filesystems.