To use multiple layouts during a single round of a UDisc event, you need to setup Groups. 

You can only setup multiple layouts per round for events with Planned Check-In. Groups are not yet supported in Casual Check-In events.

First, visit your event's admin page by following the link in the approval email or by opening the UDisc app and locating your event in the Events tab and tapping Manage

Navigate to the Setup tab and select Courses. From this page, you can add groups and give each group a name. Make sure you have added your divisions, too.

Then, go to the Rounds page. For each round, you will see your groups listed. Select the course and layout that each group will play, then assign divisions to each group for that round. Make sure that all divisions are accounted for during each round.

Finally, just click Save at the bottom of the page and you'll be good to go!