What does the folder you are about to choose contain?
Studios that exist in more than one folder
Merge them into one studio, or remove one copy. "Remove" only hides it inside Bunko; your files are never touched, and you can bring it back below.
💾 Backup
One file with your library: series, chapters, covers, reading progress and your merge / remove choices. Your image files are not included, so after importing on a new browser you click 🔗 / 🔒 once per folder to give access again.
🔒 PIN lock
This hides the screen; it is not encryption, so someone with access to your browser profile or its developer tools could still reach the stored library. If you forget the PIN: open the browser's developer tools → Application → Local Storage and delete the bunko_pin_hash entry (your library stays). Making a backup first is a good idea.