I'm not sure if this is overly helpful, but I've accomplished a work-around for a "on success, end job" function. For example, the scenario "Run Task 1, on success, exit. Otherwise, continue to Task 2." You can inactivate Task 2 (so if it's the last task it will end the job on success) then on the "on error" tab of Task 1, specify "Go to Task 2." This will still run Task 2 like you would expect.
I've only done this with a job with 2 tasks, and I realize that it wouldn't work so perfectly if there were more tasks, but I'm confident I could find a workaround for that too, given enough time.
The On Success tab would make it easier though! Good suggestion.