I need to be able to save it (not export).

I used the free version for a couple of days and purchased the pro version because I was very satisfied with the product. However, it was one major shortcoming. I have created about 6 collages and it is very painful to recreate them from scratch every time I want to change a background, border, color detail or just change one of the pictures. I would like to be able to save the collages so that I can reopen then later and make changes. The app should not save the photos but rather save a link to the original ones and load them when the saved file is opened.