You can update the order of your listing on the multiview calendar by changing the order on the Listings page.
Please go to Listings > select Listings order:
Drag and drop your listing in the order you want to have them displayed:
In the same way, you will see your listings on your multi-calendar view:
Note: parent-child listings relation will remain as one unit and you cannot split them.
Also please bear in mind that you need to do the changes in listing section with the option "Sort by" using "Listing order asc" or "Listing order desc". The order you put in each one of this options will be the listing order that will appear in the multiview calendar (also by filtering either "Listing order asc" or "Listing order desc")