Hi MM,
You’re certainly free to create items in Method and the ability is available via our stock screens. You can find this by navigating to QuickBooks > Lists > Items. You will however, need to sync to QuickBooks for various other purposes.
One example is that QuickBooks handles the application of payments. Payments are not applied to their respective invoices until both transaction have synced with QuickBooks. As a result, the balance on the invoice is not updated until this occurs.
It’s best practice to leave your sync running as much as possible and to perform a full sync at least once per week. I hope this helps.
--Audisho