Now that we can pull scans back out, it would help if the registration report had a column that showed which other scans the specific one in question is attached to. We don't always attach scans to the previous one, sometimes it was the one 25 files up. Being able to see what is linked to that file would be helpful. Maybe two columns - attached from (which file the current file was joined with) and attached to (files that were joined using the current file).
