Is there any way to save instances (for example, a map where players edited by adding buildings) in Data Stores currently?
You can save everything you need to create the instance such as size, position, class, and rotation. Save these values in a table. This is called Serialization. It's where you take an object and deconstruct it. When you need the instance again, you can use De-serialization to reconstruct it. You can not directly save instances but can save everything there is to know about it.