The first time you try to edit (add) a value in the instance variables on objects, the focus is lost as soon as you type the first character. You have to scroll back down and select the field again to finish typing. This problem doesn’t persist after a value is already in the field.
I’m running this version of GDevelop : 5.0.140 (editor full version: 5.0.140-a47ec5199eab60ac473453c8705686f737abff6a, core version: 4.0.99-0-release)