Thank you for the suggestion.
Currently the only way is to ban by IP, but in this case the widget won’t appear for that user as well.
To ban by IP, please go to Admin – Ban List – click Ban IP button.Brian commented
Just don't make it so the chat window disappears from agent's own view of their website. This makes it difficult to test things as well as confirm that your tawk.to is on / functioning properly. This is the biggest problem with filtering your own IP or banning yourself.