I would also like to know the answer to this question

Open the teleport menu, scroll locations to the right until you see Custom and there is a "New Custom Location" button.
The question is, is it possible to teleport vehicles too?

Getting a bug where the custom spawn locations vanish and I just get error messages. Can't make new ones either. Worked fine once and then when I came back the next day the problem arose. Anyone had this issue before?

引用自 Hououin Kyoma：

Getting a bug where the custom spawn locations vanish and I just get error messages. Can't make new ones either. Worked fine once and then when I came back the next day the problem arose. Anyone had this issue before?

I'm dealing with this right now. Still a problem 2 years later. Not sure what caused it or why it won't fix.. done everything but uninstalling the game and reinstalling it, which I can't do with my current internet.

So yeah
Guess I'm just stuck with it.

Custom worked yesterday and today is erroring, looking into what might of changed.

ended up fixing my custom location by validating files on project zomboid. This erases any custom locations. I'm guessing that a long name or accidental special character causes the error.