I understand the restriction on Global variables being generally available in extensions but there is one scenario where this causes real issues. This is when a page using a variable as aa field value. In these cases you can add a trigger OnAfterValidate() to know that the field have changed but there is no way to get the field value. Some good examples of this are any of the statistics pages where the PeriodType is a variable. It is impossible to subscribe to a user change as you cannot get the field value. There are a couple of ways this could be solved either the field value can get passed as part of the event of something like CurrPage.FieldName.Value to get the current value.