Compose VM with multiple NICs


Can’t find opportunity to compose VM with multiple NICs as it shown on Docs.
My installation is MAAS version: 2.6.1 (7832-g17912cdc9-0ubuntu1~18.04.1). And I’ve tried many things and still nothing, in my menu not presented Define ( Optional).

What could be wrong? How to enable this menu?

Thanks in advance!