Hi @phu.dang,
That’s a bit of a legacy field that doesn’t really affect anything in the editor user interface anymore.
It used to be the case that when users were first setting up their trigger or action, when they select App and Event, we would only display three event types (triggers or actions) and they had to click on a Load More button to see the rest. If it was set to important it could show up in the top three that we initially showed.
I thought you might enjoy the history lesson, but the answer to your question is that it doesn’t have any effect on things anymore.