Open a Design file and choose Branches from its action menu. Editors can create a Branch and update one from Main. People who manage the file can merge a Branch that is up to date with Main; a version of Main is saved first. If an update finds conflicting changes, the Branch is left as it was and the conflicts are resolved in the Web editor.
Manage Design Branches from mobile
Create Design Branches, update them from Main and merge them from the mobile app.