I think a spreadsheet and writing by yourself what's in a folder won't be a practical solution.
What kind of backup are you talking about? The pupsave files, or data folders in your computer?
The usual tools I use to backup data folders are:
To backup to local drives (or external drives mounted on my computer) rsync command with the appropriate syntax and options, you can run it by hand, writing a short script so you just click on it to run the commands, or automatically at certain time using the cron command
And, my favorite backup tool: syncthing app. It will synchronize folders between different computers, on the same local network or through the internet. It takes a bit of tweaking at first, but once it's set up, it's very reliable and transparent to the user, you won't notice it's even running, you just do anything on your local folders, and that will be replicated on the other computers. It has even versions backups, so when you delete a file on one computer, the other computers keep backup copies (as many as you set) on a hidden folder, for a specified period (it could be years of backup versions of a file if you want, and your storage is large enough). It also has backup options, so one computer (or folder) can be used as backup only, only receiving files and not sending changes to the rest of the computers.