Manages the SceneTree selection in the editor. This object manages the SceneTree selection in the editor. Adds a node to the selection. Clear the selection. Gets the list of selected nodes. Gets the list of selected nodes, optimized for transform operations (i.e. moving them, rotating, etc). This list avoids situations where a node is selected and also child/grandchild. Removes a node from the selection. Emitted when the selection changes.