Refactoring the Gravity Forms native repeater fields. Read more at https://www.gsarigiannidis.gr/gravity-forms-native-repeater/

gravity-forms-native-repeater-field-example.php

<?php
    $form_id = 3; 
    add_filter( 'gform_form_post_get_meta_' . $form_id, 'add_repeater_field' ); 
    function add_repeater_field( $form ) { 
      
      $field_id = 1000;
      $fields = [
        GF_Fields::create(
            [
              'type'       => 'text',
              'id'         => $field_id += 1,
              'formId'     => $form['id'],
              'label'      => __( 'Field 1', 'theme-prefix' ),
              'pageNumber' => 1,
            ]
          ),
          GF_Fields::create(
            [
              'type'       => 'text',
              'id'         => $field_id += 1,
              'formId'     => $form['id'],
              'label'      => __( 'Field 2', 'theme-prefix' ),
              'pageNumber' => 1,
            ]
          ),
          GF_Fields::create(
          [
            'type'       => 'select',
            'id'         => $field_id += 1,
            'formId'     => $form['id'],
            'label'      => __( 'Field 3 (dropdown)', 'theme-prefix' ),
            'choices'    => [
              [
                'text'       => 'Option 1',
                'value'      => 'option_1',
                'isSelected' => true,
              ],
              [
                'text'       => 'Option 2',
                'value'      => 'option_2',
                'isSelected' => false,
              ],
              [
                'text'       => 'Option 3',
                'value'      => 'option_3',
                'isSelected' => false,
              ],
            ],
            'pageNumber' => 1,
          ]
        ),
      ];
      $repeater = GF_Fields::create(
        [
          'type'             => 'repeater',
          'description'      => __( 'Maximum of 3 team members - set by the maxItems property', 'theme-prefix' ),
          'id'               => $field_id,
          'formId'           => $form['id'],
          'label'            => __( 'Team Members', 'theme-prefix' ),
          'addButtonText'    => __( 'Add team member', 'theme-prefix' ),
          'removeButtonText' => __( 'Remove team member', 'theme-prefix' ),
          'maxItems'         => 5,
          'pageNumber'       => 1,
          'fields'           => $fields,
        ]
      );
      $repeater_exists = false;
      foreach ( $form['fields'] as $field ) {
        if ( 'repeater' === $field->type && $field->id === $field_id ) {
          $repeater_exists = true;
        }
      }
      if ( ! $repeater_exists ) {
        $form['fields'][] = $repeater;
      }
      return $form; 
    }