Cookbook: computed display

Where in the UI. Structure expressions canvas; Layout number/text source → expression.

1. Expression graph: fieldRef amount × fieldRef valueNow (calculate).
2. Set that node as output. Name the expression “Line total”.
3. Number widget source = expression “Line total”. Leave it non-editable.

To persist the result (e.g. write into an item field), use a fieldBindings node instead of, or in addition to, the widget.