In the user exit USEREXIT_MOVE_FIELD_TO_VBKD.
I put the following code.
Move schedule line date to service rendering date.
MOVE vbep-edatu TO vbkd-fbuda.
MOVE vbkd-fbuda TO *vbkd-fbuda. "
I use VA02, It doesn't populate schedule line date to service rendering date field.
in the line item, Service rendering field still empty.