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The DockWindows (ToolWindow or DocumentWindows) have no property which stores the dock position, ot only has DockState, which tells you what it the state of a window. I suppose that you want to modify the allowed dock positions when re-docking windows. If so, you can subscribe to the PreviewDockPosition event and modify the positions for the current drag operation. Please refer to the Using the DragDropService
article for more information.
If this is not what you want to achieve, I would kindly ask you to send me a more detailed explanation what is the functionality you are after.
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