The wpcrm_system_fields filter returns an array of fields. This filter is not specific to any particular record type.

This filter can be used to add new fields or remove default fields that are not needed.

The fields are passed as an array to the filter like in this example:

 $contactFields = array(
    array(
      'name'          => 'contact-name-prefix',
      'title'         => WPCRM_NAME_PREFIX,
      'description'   => '',
      'type'          => 'selectnameprefix',
      'scope'         => array( 'wpcrm-contact' ),
      'style'          => 'wp-crm-first',
      'before'          => '',
      'after'          => '',
      'icon'          => 'dashicons dashicons-businessman wpcrm-dashicons',
      'capability'    => WPCRM_USER_ACCESS
    ),
    array(
      'name'          => 'contact-first-name',
      'title'         => WPCRM_FIRST_NAME,
      'description'   => '',
      'placeholder'   => '',
      'type'          => 'default',
      'scope'         => array( 'wpcrm-contact' ),
      'style'          => '',
      'before'          => '',
      'after'          => '',
      'icon'          => '',
      'capability'    => WPCRM_USER_ACCESS
    ),
    array(
      'name'          => 'contact-last-name',
      'title'         => WPCRM_LAST_NAME,
      'description'   => '',
      'placeholder'   => '',
      'type'          => 'default',
      'scope'         => array( 'wpcrm-contact' ),
      'style'         => '',
      'before'          => '',
      'after'          => '',
      'icon'          => '',
      'capability'    => WPCRM_USER_ACCESS
    ),
//and so on
);