Pass in a object into that has the contents to be displayed by Form2. When values change in the UI of Form2, update the object. Later after Form2 closes and another instance of Form2 is created, pass in the same object.
Basically this is the application of the concept of keeping your Model (e.g. your data) separate from your View (e.g. your UI). If you've heard of the MVC, MVP, or MVVM patterns, all of these rely on the that concept of the keeping view and data separate. The only job of the view is to reflect the current state of the model.