how to delete multiple texts messages at once on a Mac?

Do you mean individual messages? or entire conversations?

You can select multiple messages in a thread using the standard MacOS techniques (cmd-click to toggle selection, shift-click to select a range), after which you can simply delete all the selected texts.

What you can't do is select multiple conversations - Messages.app doesn't offer any mechanism for selecting multiple conversations at once, which precludes deleting them en masse.

FWIW, Ventura added the ability to delete multiple conversations at one time.

oh, cool. I missed that one.

Camelot wrote:

oh, cool. I missed that one.

I figured. 😎