Remove default WP-CRM System fields

functions.php

add_action( 'admin_init', 'wpcrm_system_remove_fields' );
function wpcrm_system_remove_fields(){
  // remove fields in campaigns
  remove_filter( 'wpcrm_system_fields', 'wpcrm_system_campaign_fields', 10);
  // remove fields in contacts
  remove_filter( 'wpcrm_system_fields', 'wpcrm_system_contact_fields', 10);
  // remove fields in organizations
  remove_filter( 'wpcrm_system_fields', 'wpcrm_system_organization_fields', 10);
  // remove fields in opportunities
  remove_filter( 'wpcrm_system_fields', 'wpcrm_system_opportunity_fields', 10);
  // remove fields in projects
  remove_filter( 'wpcrm_system_fields', 'wpcrm_system_project_fields', 10);
  // remove fields in tasks
  remove_filter( 'wpcrm_system_fields', 'wpcrm_system_task_fields', 10);
}