Why is this field parameter used?
When the parameter execute code only on add is active, it will be calculated only at the moment of addition.
For example: you have a price list and orders. When you add an item to an order, you want to get the price from the price list.
But later, when the price in the price list changes, it should remain unchanged in the order.
Will the field have an indication when this parameter is active?
No, the field will not have code field indication.
Will the field be recalculated when it changes in a row of a simple table after adding it?
No. It will be calculated only at the moment the row is added.
How do I force the code to run again when the code has "Execute code only when adding" active?
This uses action-code, for example with a button and the function recalculate with the parameter field.
=: recalculate(table: 'table_name'; where: 'id' = #id; field: 'field_to_refresh')