This has always been allowed. When the trigger fires, it will check all the parent events are true. In this case it's identical to
+ On start of layout
+ a = 0
-> actions
It allows you to reorganise events like this:
+ Trigger A
+ Condition
-> actions
+ Trigger B
+ Condition
-> actions
In to this, saving repeats:
+ Condition
----+ Trigger A
----> actions
----+ Trigger B
----> actions