In the Pulse monitor, you can see the active threads (the one which are running) and also the non Active threads (finished a few minutes ago):
If you tick the Active box, you will see only the Active threads:
With Pulse 5.3, you can now choose for how long you want to see the thread once it finishes. The setting is in the Settings tab of the About page, by default it is set up to 15 sec:
It means that once a thread finishes, it will stay 15 sec in the Monitor as an Active thread and then it will disappear.
The value has to be greater than 0.