Use case 1:

If the unpublished variant is for branch A, but the channel manager shows branch B and a webmaster modifies experience page for branch B, then first the unpublished version of branch B must be checked out and stored as preview.

Use case 2: When unpublished variant is for A and has changes only in the hst:page, then when starting to edit branch B, the changes in the hst:page must be checked in as a new version in version history!! For this see below

Conundrum

When in the Channel Manager a BRANCH is rendered from VERSION HISTORY, then all UUIDs will point to frozen nodes. When restoring the version to unpublished, are the UUIDs then maintained??? This might be a tough nut to crack. Hence raising the story points

Conclusion

In CMS-13471 we made sure that the 'hst:page' child of unpublished variant does not get replaced between draft and unpublished. As a result, also the UUID for hst:page stays the same when a branch from version history gets restored. This is very helpful!