Work is continuing on this highly requested feature. Please see the roadmap for status here: https://www.microsoft.com/microsoft-365/roadmap?filters=Microsoft%20Teams&searchterms=65332.
The ability to delete Bot messages feature has been added to the backlog. Thank you for your feedback!
We’re updating our command library all the time, so keep checking the menu in the command box to see what’s new by typing / or @.