Line type Freight in Prepayment invoice?

Summary:

Is it possible to enter a line of type Freight on an invoice of type Prepayment?

Content (required):

A supplier invoiced us for a 50% prepayment. One of the invoiced lines is for freight. When invoice header type is Prepayment, the only line types available are Item and Withholding Tax, whereas invoices of type Standard allow line types Item, Freight, Miscellaneous.

Are the available line types for Prepayments configurable? Can I add Freight to the available line types for Prepayments?

I need to be able to differentiate Freight line type from Item in my Prepayment invoice workflow rules.

Version (include the version you are using, if applicable):