"Sync by Phone" is a feature that aligns the availability settings across multiple sub-accounts or profile accounts based on the phone number assigned to them. When this feature is enabled, if multiple accounts are linked to the same phone number, their availability for chats will be treated as unified. This means that if one account is marked as available or busy, the other accounts with the same phone number will automatically mirror this status. This synchronization is particularly useful for individuals or organizations managing several accounts, ensuring that availability is consistent across all accounts linked to a single phone number, thereby streamlining chat management and enhancing the responsiveness to chat requests.