Straight to your questions:
How to hide the design tab in Visual Studio and show only the XAML tab when editing a window containing a RichTextBox control or RadToolBar?
Choose a file in your project through the Solution Explorer in Visual Studio. Right click on it and choose "Open with...". From the opened window choose "Source Code (Text) Editor" or "XML (Text) Editor" and click on the "Set as Default" button. Next time when you try to open the same file the Designer won't be opened. Sometimes you need to restart Visual Studio in order to have the change applied. If you want to go back to the default Visual Studio's behavior, just repeat the described steps but choose "XAML UI Designer".
If you have switched off the designer, if you want to open it, you need to right click on the file and choose "View Designer".
How to disable the interactivity of the editor so that normal keyboard navigation in the XAML source code does not move controls on the WPF window?
I am not sure what you mean by this. Please note that it is important where the focus is - in the designer or in the source code editor. If you do not want to have the SmartTagPanes opened (check the attached screenshots) which are part of our design time support, the easiest way that comes to my mind is to reference our binaries from a folder where only the needed binaries are copied and not from the telerik installation where you have the design binaries also.
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