The more I'm working on this, the less I like it.
My suggestion is to add a new operation property to specify scope:
Execute when        [Event Occurred ↓]
Apply to            [Event][Window]
Type of calculation [...]

(or [Current Event][All Events])
Depending on ‘exectue when’ this property would be preselected and disabled:
Event Occurred - Event
Event Added, Event Evicted, Event Closed - Event, Window
Window closed, Pattern matched - Window
This would be more intuitive than having additional operation condition. It also explicitly shows what ‘execute when’ can be applied to current event and what to the all events.
This would allow to flag operations in list with corresponding icons - one/all events. This is quite useful information, which would be hidden inside operation details otherwise. And no operation condition pollution.
The ‘current event’ operation condition could be left as proposed, in the case user would want to apply operation to all events except the current one.
Is it too late to change database schema ? If not - I'd rather ‘hack’ the flag into ‘execute when’ value rather than specify scope through operation condition.