How do I export a team for offline play? This should be possible but I can't find the command anywhere. Has it been removed? If so, could we get it back, please?

Your team is automatically exported, once you have created a team online, you can use it offline.

Example : if you created a Light Wizards team online
Go in offline mode and choose Light Wizards in the first roll,
and in the second roll, instead of choosing the Doom Forgers, you can choose your online team.

Hope it answers to your question