There is a way to open a different archive when starting The Archive app from the Terminal.

$ open -n /Applications/The\ Archive.app --args -archiveURL "file:///Users/YOURUSER/path/to/notes/"

For example, I can open my Running Lists folder with this command.

$ open -n /Applications/The\ Archive.app --args -archiveURL "file:///Users/zsbenke/Documents/Running%20Lists/"

This will open a new instance of The Archive app. I’m not sure if that’s intended behavior, but it works for quick checks.