doc issues in event-trigger-matrix.html

hi.
I think the "X" and "-" mean in this matrix [0] is not very intuitive.
mainly because "X" tends to mean negative things in most cases.
we can write a sentence saying "X"  means this, "-" means that.

or maybe Check mark [1] and Cross mark [2]  are more universal.
and we can use these marks.

"Only for local objects"
is there any reference explaining "local objects"?
I think local object means objects that only affect one single database?



[0] https://www.postgresql.org/docs/current/event-trigger-matrix.html
[1] https://en.wikipedia.org/wiki/Check_mark
[2] https://en.wikipedia.org/wiki/X_mark