I would like to make a suggestion with the additional add of layers or sets. Currently all are viewed as one big "set" or group. The user can ofcourse rearrange everything to its own liking.
But being apple to make sets, so when you order them they also ordered in sets. These sets work a bit the same like artboards in photoshop or illustrator. Possibly it would need to GUI and show a name then i guess. Another option could be than that sets/groups are colored by group/set, so each have there own color.
Another approach could be layers. Its sort of the same approach but than with layers, so groups of images are ordered with layers.