You don’t run terminal-notifier . Joplin sends a notification and internally terminal-notifier is used. I only told you about terminal-notifier , because Joplin does nor show up in Notication Center.
So, if you want to change the behavior of Joplin’s notifications, you will have to change the settings for terminal-notifier in the Notification Center.

I don't know how to do that. How do the notifications appear then? If they are not in the notificatin centre, out of curiosity.