Source code for https://victorfont.com/add-multiple-fields-formidable-forms-drop-downs/

add_multiple_fields_dropdown.php

<?php
    
/* add multiple fields to Formidible standard dropdowns */
add_filter('frm_setup_new_fields_vars', 'customize_dfe', 25, 2);
function customize_dfe( $values, $field ) {
    if( $field->id == 125 ){ //Replace 125 with the ID of your data from entries field
        global $frm_field;
        $values['form_select'] = 3441;
        $field4_opts = FrmProFieldsHelper::get_linked_options( $values, $field );
        $values['form_select'] = 3428;
        $field3_opts = FrmProFieldsHelper::get_linked_options( $values, $field );
        $values['form_select'] = 3430;
        $field2_opts = FrmProFieldsHelper::get_linked_options( $values, $field );
        foreach( $values['options'] as $id => $v ) {
            $sep2 = ($field2_opts[$id] !== null && $field2_opts[$id] !== "") ? ", " : "";
            $sep3 = ($field3_opts[$id] !== null && $field3_opts[$id] !== "") ? " | SSN: " : "";
            $sep4 = ($field4_opts[$id] !== null && $field4_opts[$id] !== "") ? " | State ID: " : ""; $values['options'][$id] .= $sep2 . $field2_opts[$id] . $sep3 . $field3_opts[$id] . $sep4 . $field4_opts[$id];
        }
    }
    return $values;
}

add_multiple_fields_dynamic.php

<?php

* add multiple fields to Formidible dynamic dropdowns */
add_filter('frm_setup_new_fields_vars', 'customize_dfe', 25, 2);
function customize_dfe( $values, $field ) {
    if( $field->id == 125 ) { //Replace 125 with the ID of your data from entries field
        global $frm_field;
        $values['form_select'] = 3441;
        $field4_opts = FrmProDynamicFieldsController::get_independent_options( $values, $field );
        $values['form_select'] = 3428;
        $field3_opts = FrmProDynamicFieldsController::get_independent_options( $values, $field );
        $values['form_select'] = 3430;
        $field2_opts = FrmProDynamicFieldsController::get_independent_options( $values, $field );
        foreach( $values['options'] as $id => $v ) {
            $sep2 = ($field2_opts[$id] !== null && $field2_opts[$id] !== "") ? ", " : "";
            $sep3 = ($field3_opts[$id] !== null && $field3_opts[$id] !== "") ? " | SSN: " : "";
            $sep4 = ($field4_opts[$id] !== null && $field4_opts[$id] !== "") ? " | State ID: " : ""; $values['options'][$id] .= $sep2 . $field2_opts[$id] . $sep3 . $field3_opts[$id] . $sep4 . $field4_opts[$id];
        }
    }
    return $values;
}