The Keep catalogue files after uninstalling catalogues option means that if you turn off a catalogue from the Catalogue Details, or simply uninstall an extension that has ties to the manufacturer’s catalogue, then catalogues will be hidden in CET Designer but the downloaded data will not be removed from your local drive.
Checking the option Append option code in property box if available will have the option code of the catalogue shown in the property box.
Catalogue Language Override
The Catalogue Language Override replaces the CET Designer default language (set in the Region tab of the Control Panel) by forcing the installed catalogue(s) to change the default language to that of the selected language, if available.
Changing the download location allows CET Designer to re-download currently available offline catalogues and project files that are in used to the new download directory. The downloaded data in the old location will not be removed, but you can choose to copy the existing data manually to the new download location. The reason behind this is that not all downloaded data are necessarily needed in the new directory.
Please note that network drive, workgroup extension storage, and external drives are not supported as download locations. The Available Space shows the free space of the selected storage location. A warning is shown if you try to change the download location to a disk slower than the current ones.