You can set the maximum number of simultaneous chat request an operator can get. Once the queue limit has reached, the visitors will be asked to leave a message to contact the operators again. 

Content Moderation

You can moderate your chat by filtering abusive content. Enabling this can help you have a professional and safe workplace to assist genuine users and avoid abusers.  

• In Settings > Brands > Your brand > Flow control, move over to the Abusive Content Moderation tab on the top, and enable the Content Moderation option.