'C:\Users\<User>\AppData\Local\T_Backup\T-Backup.vshost.exe_Url_ntrrxa4iaqozobnbkaxrvqewuh5giwdw\1.0.0.0'
or something similar. (The last bit may change slightly.)
I found the user.config file on my system. I use Windows 7 64bit so it was easy to find. The interesting thing is that there were 2 folders and 2 config files on my system.
C:\Users\<User>\AppData\Local\T_Backup\T-Backup.v2.0.exe_Url_l4jkancwjp1uwmrfpojb1bwpvoowkpel\1.0.0.0\user.config
and
C:\Users\<User>\AppData\Local\T_Backup\T-Backup.v2.0.exe_Url_ugwmpedmsygwabk25v03r01vc4dvwibw\1.0.0.0\user.config
They both contained the exact same data and date created timestamp.
This is just another interesting thing that piqued my curiosity. I would ask you for the source code of the program but that wouldn't do me any good. I can only understand very basic coding languages like html and javascript. My LUA is minimal. I can understand most of it but not actually make code that works. I am learning it though.
The thing I am thinking of for multiple profiles (a quick dirty option) is to just create multiple user.config files and make a bat file to move them back and forth into the correct folder. This is a simple way to make it work until you figure out multiple profiles.
Another huge thank you for making this program. I backup my players and worlds every time I play. It is so convenient. I have had to use the backups too.
One last thing I am wondering is if the player and world backups would be able to be created while Terraria and the world and character file is loaded and running. I'm guessing no so I have been shutting down Terraria and making a backup then reloading it up to be safe. I don't know enough about how and when Terraria writes data to the world and character files when it is running. I expect corrupted backups but more testing would be needed for me to confirm that. The reason I'm looking into this is because I have to shut down the "Host and Play" world and force everyone to reconnect if a backup is needed. It is a minor inconvenience but it would be neat to be able to backup the world while it is running. It might have something to do with the autosave option. I will mess around with it later.
If you read this Wall of Text, I solute you!!