Thank you for your question.
Actually this is a not yet implemented functionality. When a floating window is hidden and then persisted, it is moved to its the ToolTabStrip that holds its Docked state. We are aware of this missing feature and we will do our best to implement it in some of our next releases.
I have logged this as a feature request
in our Public Tracking System (PITS) where you can track its progress.
Your Telerik points are updated as a token of our gratitude for your feedback.
All the best,
the Telerik team
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