Class - its a description of some data instance. Class itself can contain only static variables (and you cant create static in BP, afaik, only C++), all non-static variables exist only inside class instances, not in class itself.
You need to create instance of class (if its a actor class - you need to spawn actor, if its a widget class - you need to “create widget”) to access that variables.
You try to store some global data in a widget? Bad decision, i think. Place it inside GameMode or GameState.
“set a variable on a widget that has been added to a scroll box” - Widget created? Use pointer to widget returned by “Create” block instead of class pointer.
Blue node “Return value” - pointer to instance, use it instead purple node of class