If the Project View "To Invoice / Invoiced" is pointing to Actuals, but you would need to invoice the Budgeted instead, then you need to modify this view accordingly for those particular projects.
See more details about Project Views in chapter 'Setting up the Actuals and Budgeted views'.To do this, click Show View Filters in the eye menu inside the Edit Project window, unlock the view and tick the appropriate check boxes.
View Filter setup
Part Invoicing Global Budget Operators is not supported yet, because its value depends on the rest of the Budget. If you would Part Invoice it and then continue working on the Budget, its value would change and would then need special handling to get the difference invoiced.
Forward Actuals To Budget Details
This option is useful if you are invoicing what you budgeted, and want to incorporate some extras into the Budget at the end of the Project. Or if you want to first book the project and then generate a Budget from what you booked.
In the Budget window, select one or more Actuals that are already attached to the corresponding Budget Accounts in an Active Budget, right-click and select 'Forward Actuals To Budget Details' from the drop-down menu.
Forward Actuals To Budget Details
This will take the info (Object, Quantity, Buy, Sell) from the Actuals and create corresponding Budget Details.
Budget Details created from Actuals