Hello, @toddlerner.
We can't sync contacts from the Mac address book. But, we can import the Customer/Vendor list in order for the contact to be added in QuickBooks Online.
Here's how:
1. Go to Settings. Then, select Import Data.
2. Select Customers or Vendors, depending on which you are importing.
3. Select Browse to upload the file from your computer. Choose the file, and select Open.
4. Or, to upload from the Google Sheets, select Connect to sign in to your Google account. Choose the file, and then Select.
5. Select Next.
6. In Your Field column, select each small arrow icon. Then, match your field to the corresponding QuickBooks Online field.
7. Select No Match if you have a field that doesn't have a matching column in your spreadsheets.
8. Confirm your contacts. Uncheck any you don't want to save.
9. If everything looks good, select Import.
Please refer to this article to learn more on how to import customers or vendors from email contacts to QuickBooks Online.
I've included an article that'll help you keep track of your vendor transactions in QuickBooks Online: View Vendor Transactions.
Keep your post coming if you need more help. I'll be here!
