This filter is used to enable the display of the option for dynamic field mapping under the ‘Line Items’ setting on the Freshbooks feed. Dynamic field mapping allows you to map form fields to the line item’s unit cost and quantity.
add_filter( 'gform_freshbooks_enable_dynamic_field_mapping', '__return_true' );
This hook has no parameters.
This code should be placed in the functions.php file of your active theme.
This filter is located in class-gf-freshbooks.php