Thank you for sharing your feedback. Currently, RadGridView does not suggest such a built-in functionality.
In order to detect the Ctrl + F combination and show a search window, I can suggest you is to handle the KeyDown event of the grid.
The content of the control may be a custom user control that will be responsible for searching the items. As an example you may take a look at this blog post for a reference. In your case the searching TextBox should be defined in your custom user control.
sender, KeyEventArgs e)
(e.Key == Key.F && Keyboard.Modifiers == ModifierKeys.Control)
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