how do you plan to use exported files? is that for reporting purposes or is that because you do not have some functionality within SolarWinds IPAM and you doing some post-editing in Excel?
Report can be customized via Advanced Report application that comes with IPAM. IPAM itself is not primarily focused on rich exporting options because we are focused primarily bring functionality into IPAM instead let users to manage IP addresses in multiple software.
This is something I was also wondering how to do. I have a site with 80+ subnets which I was wanting to export, open in notepad++ and do a find & replace then import back in but none of the folders and values seem to be exported as part of it.
On a side note being able to create a report with the "Folder Name" as a field would be very useful for grouping as per the OP
If you have any sql confidence you can build a trigger or job to update groupattr based on parent id attributes. It's slightly more difficult since its a join back to itself in the update statement but still a basic tsql statement.
Message me if you want any pointers...