Create a Saved Print. That will preserve the layout and your images in a specific collection.
I have made an exported print. What is a "saved print?" I see no new collections in the list of collections. Sorry - do not quite understand... thanks for your replay.
When you design a custom layout for a print collage, you can do two major things-
1. Create a "Saved Print" by clicking on the tab above the window. This saves the print design AND the photos you have used as a Collection in the Collections panel. You can return to the same print at any time, or add other photos to this collection to use the same layout
2. Save the layout as a template (for later use). This template will appear in the "Template Browser" panel and can be used with any photos you select from the Library.
So to create prints in future you can select photos, select the template (you created) and print to printer or print to JPG as you wish.
Creating a template like this is useful for designing your own Book Pages when you want a collage that is not available in the Book page templates.