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A widget is a UI component such as the inventory window or item container window. A widget's layout is grid-based and contains child elements that either display information to the player (e.g. the player's health or description of a quest) or allow the player to interact with them (e.g. a button that triggers a script or a slot for placing an item into). Custom widgets can be created in the Widget Editor.
(Accessing elements within a widget to change them or get a value from them)