Items 1 - 3: This is exactly how the program is designed to work. The process you described converts uninvoiced assets in the Billable time and Billable expenses accounts into assets in the Accounts receivable account. In doing so, it interacts with the Billable Time, Billable Expenses, Customers, and Sales Invoices tabs. And it transfers income from Billable time - movement to Billable time - invoiced. It also involves the automatic accounts Billable expenses - invoiced and Billable expenses - cost. In other words, the process involves six automatic accounts and four tabs. This far more complex than creating an ordinary sales invoice. Once the invoice is created, however, it can be edited like any other invoice.
Item 4: What do you mean by this? Debits and credits are not listed in the Billable Time tab.