How to determine which master key is "active"

According to the E2EE documentation:

Only one master key can be active for encryption purposes. For decryption, the algorithm will check the Master Key ID in the header, then check if it’s available to the current app and, if so, use this for decryption.

If I have multiple master keys loaded into Joplin on iOS, how can I tell which master key is being used to encrypt a note? Is it always the one with the most recent time and date stamp in “Encryption Configuration”? Is there an option that I’m missing?

Thank you all for your time. Joplin is really cool!

Yes, the one with the most recent timestamp.

Thank you for your super fast response; wow!

Would it be possible to allow the user to select which key to use, or perhaps to “re-key” a note to the most recent key? If someone is worried that a key might be compromised, it would be nice to be able to “re-key” the database.

Thank you for making such a cool application!