Yes. You can copy the amounts from Excel and paste them straight into the production value column in Billing Schedule Client. That way you don't have to type in each installment.
How to do it
Open the Excel sheet with the billing schedule.
If the months run across, the amounts must first run down. Copy them, and use Paste Special → Transpose in Excel.
Copy the amounts that now run down.
Go to Billing Schedule Client and click the name of the billing schedule. Select the Production value tab, where the months run down, and click the first cell in the Production value column.
Paste.
Check that the amounts ended up on the right lines.
Good to know
Copy only the amounts, not headers or totals.
The order in Excel must be the same as in the billing schedule.
You can also paste accrual from Excel in Setup and Operation.