When I do apply for audio effects in one event I can`t go back and change it if I want to. Is it a place where I can see that I have added a audio fx, like the one for the entire track??
no, when you apply a non-realtime effect, it is permanent, so there is no record of that.
you could put the events you want to effect on their own separate track, then apply the effect to that track. that will allow you to go back and make changes.
When you add a non-real-time effect to a track, make sure to save it with a different file name. That way, you can go back to the original if you need to.