How are we supposed to play expanded?

In deck editor, there should be a button saying Standard on the top left corner. If you click/tap that, it turns into Expanded. The only way I know to play expanded (I haven't tested Expanded in Battle) is to go to Casual and there should be two buttons in the middle. One should be red and mostly cover up the second, that one is Standard. The second is blue and says Expanded. If you click/tap Standard it switches to Expanded

You can barely play Standard. Just pretend that Expanded rotated, because those cards are probably never coming.