The problem is that you are saving a REFERENCE to the object (object path), not the widget itself. Your save file should store the DATA from the widget (texts, image links, etc.) that you can use to “recreate” the original widget.
Serialization will help with this in the most automated way, but you will need minimal knowledge of C++.
But in principle you can limit yourself to blueprints only, you will just need to create many variables for different types of data…