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I need option to prevent window switching, while I'm using keyboard. Thanks.

You mean something like the "focus stealing prevention" that already exists in your KDE configuration?

Maybe. Give me hint, where can I setup this and i give you access to remove this topic.

I thought focus stealing prevention isn't case of keyboard, but rather mouse.

Open your settings dialog, type "focus" into the search field and Tada! you have a single entry left in the menu.
Was that really _that_ difficult?