Yes - Fold Plus subscribers can now connect more than one Gmail account, so credit cards across different inboxes can all sync on Fold. To add another Gmail account, go to Profile and tap Emails under Secure connections. You can also pick the right Gmail account while adding a new card.
If you're on the free plan, Fold connects a single Gmail inbox. You can still track cards across inboxes by auto-forwarding everything into one Gmail account and connecting that to Fold.
To set up auto-forwarding you can follow the guides below: