If you want to use the location field from Google Calendar inside your reminder messages you can use the token $CUSTOM3. It does not HAVE to be a location. It can be anything like a name or meeting place. The system will take whatever you write in the location and add it to the script when you set it up as such.

So you could say something like:

Hello this is a reminder that we have a schedule visit on $APPOINTMENT_DATE_SHORT - $APPOINTMENT_START_TIME at $CUSTOM3. Please visit $REPLYLINK to confirm or reply with Yes.