Sorry, I have no idea what you mean by saving scene as an image (?) to a PNG file and thinking OBS can do anything with an image in terms of settings import/save/recall?
There is a native feature for Scene Collection import/export. Don't change the file extension.
However, when you work on scenes, that is auto-saved and will be there next time.
So why do you need to import in first place unless
- moving to OBS on another computer (or user profile on same PC)
- or, you saved a scene collection, made changes or new, and now want to go back
side note - you can made multiple scene collections and pick between them with no need to import/export (save/recall)