Hello @bjoern, thank you for taking the time to share your thoughts.
Projects are saved in the app storage, yes. I'm not sure if you're aware of the Export > "Image Sequence" function, but that effectively makes a copy of the project to your device storage. So, as long as you haven't deleted the projects in the app (or moved the folders from the app folder), then you can always re export them. Does that solve your use-case?
(I'm also aware that for auto sync to DropBox, etc. this isn't ideal and I have it on the roadmap to look into how this could be done.)