Load predefined JSON files by their name, then make the list accessible to child themes

child-functions.php

<?php
class craft_child_features {

  static function setup() {
    add_filter( 'craft_acf_parent_features', __CLASS__ . '::craft_child_remove_acf_groups' );
  }

  /**
   * [craft_child_remove_acf_groups description]
   * @param  [type] $features [description]
   * @return [type]           [description]
   */
  static function craft_child_remove_acf_groups( $features ) {
    // Remove ACF Groups from parent
    // var_export( $features ); // Uncomment to see the available features
    $ignore_list = [
      'variation-gallery',
    ];

    // For each item in the array, remove the key from features
    foreach ( $ignore_list as $ignored ) {
      if ( ( $key = array_search( $ignored, $features ) ) !== false ) {
        unset( $features[ $key ] );
      }
    }

    // Add new groups / files
    $add_list = [];
    // If there files available, merge that with the features list
    if ( ! empty( $add_list ) ) {
      $features = array_merge( $features, $add_list );
    }

    // Return the available features for this theme.
    return $features;
  }
}
}
craft_child_features::setup();

functions.php

<?php 

class craft_features {
  
  static function setup() {
    add_action( 'acf/include_fields', __CLASS__ . '::craft_acf_add_features' );
  }
  
 /**
   * [craft_acf_parent_features list all features in parent theme]
   * @return [array] [list of filenames for acf-json to use]
   */
  static function craft_acf_parent_features() {
    // A list of the file names and their features
    $features = [
      'content-builder',      // → Layout and content builder
      'menu-builder',         // → Main / mega menu builder
      'theme-settings',       // → Theme settings
      'banner-builder',       // → Banner builder for banner CPT
      'banner-layouts',       // → Banner layouts for banner CPT
      'banner-groups',        // → Banner Groups for banner group taxonomy
      'brand-logo',           // → Brand logo on Brand Taxonomy
      'variation-gallery',    // → Variation gallery on single product variations
    ];
    // Give me that list
    return apply_filters( 'craft_acf_parent_features', $features );
  }

  /**
   * [craft_acf_add_features Add all the features to the current theme]
   * @return [acf-json] [Add the ACF group to the website]
   */
  static function craft_acf_add_features() {
    // is ACF loaded? Does it even exist?!
    if ( ! function_exists( 'acf_add_local_field_group' ) ) {
      return;
    }

    // Craft path for acf json
    $child_path  = untrailingslashit( get_stylesheet_directory() . '/acf-json' );
    $parent_path = untrailingslashit( get_template_directory() . '/acf-json' );

    // A list of the file names and their features
    $features = self::craft_acf_parent_features();

    // For all these features, load it all in.
    foreach ( $features as $feature ) {

      // Create the file paths + add .json to it
      $file = $child_path . '/' . $feature . '.json';

      // If the file doesn't exist in the child
      if ( ! file_exists( $file ) ) {
        $file = $parent_path . '/' . $feature . '.json';
      }

      // Check the parent, skip if not found
      if ( ! file_exists( $file ) ) {
        continue;
      }

      // Is this a json? Lets double check.
      $json = file_get_contents( $file );
      if ( empty( $json ) ) {
        continue;
      }

      // Load the JSON into the theme
      $json = json_decode( $json, true );
      $json['local'] = 'json';

      // Check if we haven't loaded this already
      if ( acf_get_field_group( $json['key'] ) ) {
        continue;
      }

      // Create ACF field group based on json
      acf_add_local_field_group( $json );
    } // end foreach
  }
}

craft_features::setup();