there is no GUI option to update the "External Routes" for an External Segment

[Kent Wu]

When you create an external segment thru GUI, there is a section for you to add the external routes. However once that's done, there is no GUI option/page for you to update that external routes....You can only do that thru CLI command like:

gbp external-segment-update <> --external-route destination: <>,nexthop: <>

As a matter of fact, pretty much all the options available (IP version, CIDR, subnet ID, ...etc) while creating a ES is not there when you try to update an ES.....