It's a great question, Winnie9628. The "Clients" under Bookmarks refers to QBO Accountant firm-level clients (companies you manage), while "Customers" under "Sales" are the specific customers/clients you invoice within a single company file.
When you create a name while entering an invoice, QuickBooks automatically adds it to your database. However, they won't appear in the 'Clients' bookmark because that area is reserved for 'Client Files' (the businesses you provide bookkeeping for), rather than the individual people you are billing.
To see the customers you just created, head over to the Sales tab on the left menu and select the Invoices. You’ll find your full list there, along with their open balances and transaction history.
Let us know if you have more questions or need further assistance.
