So... simple question I can't find. I created a custom record type, but that custom record type is not showing up under the classic menu under Lists -> Custom, even though a different custom record I created is. What's the secret to getting the custom record to show up under Lists -> Custom ?

path to custom records is customization>Lists, records & Fields > Record Type - for Classic center. If you are looking for direct link to that custom record then you have setup the link in custom record's record under the link tab see below

@Sam-I-Am got it. Thanks, that's what I was missing.