With all the changes in the languaje, maybe that is a good thing.
If the variable IS IN the open event, it is local to that event.
Currently Your only options are the documentation or the youtube channel:
And a side note, talking about scope, it is weird, some one from Xojo wrote a couple days ago that the scope of things it was a super davanced topic that newbies didnt need to understand
if you speak about a container control with other controls inside you can use computed properties.
it have default scope public.
as example
var a as string = mycontrol1.mycomputedpropertie
mycontrol1.mycomputedpropertie = “Hello”
computed propertie have a get and set method there you can return a textfield.text or write into.