Not quite. It lives in ~/Library/Application Support/Plex Media Server/. That squiggle-slash at the front means “your user’s home directory.” In Finder, click Go then hold the Option key on your keyboard; then select Library in the Finder list on the left. That will be your user’s Library folder. From there you can navigate to ./Application Support/Plex Media Server/.
Haha, indeed. I had a specific reason for going with the wording I did, but it’s not really important . Taken to its logical extreme, I probably should have gone with “squiggle and forward-angled-verticle-line.”
At any rate, I hope it helps the OP find their wayward Plex data directory. I’m sure it’s there somewhere.