Whenever you install an SDK version, the extension calls west zephyr-export to store information about the installed versions in Zephyr's CMake registry. This registry is used to add entries to the Uninstall SDK menu in the Welcome View. However, this storage mechanism only applies to SDK versions that are installed and managed through the extension.
Repository and workspace applications come with their own SDK versions in their own workspaces. If you add such applications to the extension, the extension does not store information about their SDK version in Zephyr's CMake registry. Because of this, they are also not listed in the Uninstall SDK menu. This prevents breaking repository and workspace applications if the corresponding SDK version were to be uninstalled using this menu and removed from Zephyr's CMake registry.
For more information about how different application types handle SDK versions, see Applications.