Custom fields in TB are mapped into the ones in Google with the labels Custom1 - 4. Don't modify the labels in Google otherwise they cannot be sync.
Summary of the changes in v0.6.30b1 are the following:
- Birthday field sync
- Nickname field sync
- Web Page fields sync
- Custom fields sync
- Option to derive First Name and Last Name from Display Name; it is done by Google server and the correctness depends on Google.
- Cannot copy/move cards from an Google account to another Google account
- "Reload before sync" message pops up when sending a message
- Fail to sync if a card is modified several times