Yes, just make sure you are logged into your customer account. There you can save your collages, as well as projects anytime, and come back for further edits whenever you want.
You will then find saved collages in your customer account under “My collages”.
In the Collage Designer, you can also access your saved collages directly via the “Projects” button.
Customer Account: 'My collages'
Collage Designer: My Projects