Unfortunately we don't know of any easy way to export from Google Authenticator, though if you are using another 2FA app they may have better export options.
The best process at the moment appears to be to login to each account, disable 2FA, then re-enable it and use Strongbox to store the new codes. Strongbox can scan QR Codes generated by the sites when you re-enable 2FA. Here are some helpful articles on how this process works.
https://www.wired.com/story/how-to-switch-from-google-authenticator-authy/
https://lifehacker.com/how-do-i-switch-from-one-2fa-authentication-app-to-anot-1842296754
To add a TOTP code in Strongbox on iOS just:
- Unlock your database
- Tap the More icon (in the top right of the screen)
- New Entry
- Setup TOTP