Edit: Resolved:
The details for this are located in the AppData folder on Windows, specifically this file:
%AppData%\Steinberg\Cubase 12_64\Defaults.xml
Simply deleting the file and re-starting Cubase resolves the issue, however this will revert a number of configurations, such as plugin defaults and other default settings.
To resolve without doing so, close Cubase completely then open this file and search for
mediaBrowserAddTrackDialogTrackTemplate
Above it there should be an <item> tag. Delete everything between the <item> and </item> tag far below (including the two tags).
Repeat if there are more than one instances of this section in this file.
Save the file, then reopen Cubase and it should be fixed.
Original Post:
Only seeing my own saved track presets. Not sure what happened to all of the factory ones. I have all of the factory content installed (on an external drive, which is connected), but my track presets folder looks like this:
