Location of data
Config file
The settings typically get written to ~/.config/Bouquin/Bouquin.conf.
Database file
The default database for your notebook is stored in ~/.local/share/Bouquin/Bouquin/notebook.db. This is an encrypted SQLCipher database, you can't open it with a normal sqlite CLI tool or other DBMS.
You can choose a different database file to open when starting the application (unless you have set Bouquin to remember the Encryption key). Bouquin remembers this path and saves it in the config file so that you don't have to keep selecting that database each time you start the application.
If you have set Bouquin to remember the Encryption key but wish to open a different database, first open Bouquin, navigate to the Settings and uncheck 'Remember Encryption key'. Next time you open the app, you'll be prompted for both the database path and the key as normal.