No, I don’t think you want to do that. That would mess a lot of things up and would be very hard to revert.
Deleting the last post, resetting the bump date, and then undeleting the post can be a good workaround.
There’s also the option to not bump the topic in the composer itself when adding a reply, in the composer options menu in the top left.
Edited to remove Jammy talking nonsense
Resetting the bump date will take it back to the last activity of the topic preceding the latest change. If you’re only adding one post, resetting should take it back to the point before that. Make sure you refresh the topic list to get the current view that reflects the change.
If you add a post and then close, resetting would take it back to the post you added. In those situations I delete both the post and the close small action post, reset, then undelete both again.