This snippet is an example of how to programmatically set a default selected value in a dropdown and multiple choice field in WPForms.

wpf-set-default-option-value.php

<?php

add_filter( 'wpforms_field_data', ( $field, $form_data ) {
 
    if ( absint( $form_data['id'] ) !== 2067 || absint( $field['id'] ) !== 5 ) {
        return $field;
    }
	
    $default_field_value = 'Second Choice';
	
    foreach( $field['choices'] as $key => $choice ) {
        if( $choice['label'] === $default_field_value ) {
            $field['choices'][$key]['default'] = true;
            break;
        }
    }
 
    return $field;
 
}, 10, 2 );