Scope: managed applications.
When you develop form logic, keep in mind that if in 1C:Enterprise mode users add form items (All actions - Change form), these items cannot be accessed from 1C:Enterprise language.
For example, if a user adds a page to the Group form item of the Pages kind, whenever you navigate to this page, the CurrentPage group property is Undefined. The CurrentItem form property will also be set to Undefined if an item added by a user is an active form item.
For example, instead of directly access group item properties with pages:
CurrentPageName = Items.GroupWithPages.CurrentPage.Name;
Preliminary check for Undefined:
CurrentPage = Items.GroupWithPages.CurrentPage;