Yes, as I have explained in my previous post:

macOS : >= 10.8 or Growl if earlier.

This means that you need Growl for macOS releases earlier than macOS 10.8. You are using High Sierra, not a macOS version prior to 10.8. So you are not supposed to use Growl.

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.

This is normal, because you have to create it. The first line of the instructions says:

Add a file named "flags.txt" in the config directory

open a terminal and enter the following comnand (on one line - discourse might have added a line break):

cd ~/.config/joplin-desktop && echo "--open-dev-tools --log-level debug" >flags.txt

Done.

I'm sorry, but I'm starting to wonder, if you read the text as it is written or if you just pick and choose a few words from the text. You asked questions again that I have already explained in my previous post. I'm not sure what else I can do. I think I have expressed myself rather clearly, so I'm at a loss.