I found the documented variables from a post by Chris_B:
It is in the help file with ISOGEN (...\CADWorx 201X\Plant\ISOGEN\ISOGEN_Releases.chm Search for "Dynamic File Naming")
Another route is to model your lines with the iso output you need.
Or if you need to keep your line numbers, you could look into ISOWorx. We have a rename feature.
ISOWorx