Use the Programs and Features dialog to locate the Unitscape entry. Use the uninstall option to uninstall Unitscape for Unreal Engine.
If you don't plan on re-installing Unitscape and you installed the Content Library you may have to manually delete the "External Content"
shortcut at Program Files\Epic Games\UE_4.26\Engine\Plugins\Ephere\Unitscape\Content .

This will not delete the external Unitscape content library, which will have to be manually removed as well(if desired).

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