If all the processes had the same name, you could use "killall".
But as far as all created since time "X", I've never ever found a use for that. Usually I want to pick a root process and kill all its children, not kill possibly unrelated apps and services that are just minding their own business. Of course, one of my favorite apps to kill that way is Firefox, since its cache can get very, very greedy, and that's AFTER I put limits on it.
An IDE is no substitute for an Intelligent Developer.