@Diderik Would you mind to share some of the code that is not working?

This is the code

//Arbitrary rate
const rate = 123;

// Its the last item on the transaction
const lineCount = currentRecord.getLineCount({ sublistId: "item" });
currentRecord.selectLine({ sublistId: "item", line: lineCount - 1 });

currentRecord.setCurrentSublistValue({
  sublistId: "item",
  fieldId: "rate",
  value: rate,
});

currentRecord.commitLine({ sublistId: "item" });

To be able to change the line rate in most transactions you need to first set the price level to custom: fieldId: “price”, value: -1

Ah thats interesting, I will try that. Thanks!

.setSublistValue({
    sublistId: 'item',
    fieldId: 'price',
    value: '-1'
});

My bad is an string ^^^

Thanks! After a bid of fiddling I got it to work, albeit in a vacuum of sorts. The use case I have for this is having a checkbox that triggers a fieldChanged event that builds the BOM based on some info the users have filled in. In some cases however the rate changes based on the quantity of the item. So while adding all the items I want to change the rate. If I execute the code then, I still get the error I mentioned. But if I execute the code in a different fieldChanged event after all the items have been added it does work. Also why my BOM-building function is running the BOM doesn't change in the UI, only after the function has completed. And if during the function I use

findSublistLineWithValue

to get the line of the item I just added I get -1. So it feels like it can't properly access the sublist or something