From current form to previous form

you can store that value in settings... for that
open your project properties....
select Settings tab and enter your variable name, Data Type of variable and select scope as user and last if you want give any default value then give it...
after that create one property to access that variable create this property in both form or you can create one static property for that in common static class...

public string FirstValue
{
    get { return Properties.Settings.Default.DestinationPath; }
    set
    {
         if (value != Properties.Settings.Default.FirstValue)
         {
             Properties.Settings.Default.FirstValue = value;
             Properties.Settings.Default.Save();
         }
    }
}

create other variables as per need of your application...
and access it directly or use it through property that you have created before...
now you can access this variable from any form of your application...
Thanks & Regards,
Punit Parmar

The best way to form collaboration is implementing appropriate interface by the form class.
Please see the details in my past solution, see also other solutions and discussion:
How to copy all the items between listboxes in two forms[^].

—SA