Last send message in chat can be deleted for some time after is was sent. To do that you need to hover over your last message and hit small X on right side. On mobile not so easy to do. To make it mode user friendly you need to add/modify css:

.joms-chat__message-actions {
	display: block;
	right: 4px;
}
.joms-chat__message-item.you .joms-chat__message-body > div .joms-chat__message-actions .joms-icon {
    fill: red;
}

Privet Vladimir.

Thank you for sharing this :)