Can't custumize horizon dashboard in RHOSP 12

We follow the procedure to customize dashboard (https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/12/html/introduction_to_the_openstack_dashboard/dashboard-customization) but the file _99_customization.py (/usr/share/openstack-dashboard/openstack_dashboard/enabled) does not exist, are there other document where we can find the correct procedure?
Thanks
Oscar