Already addressed.
With a mortal person you can look them in the eye in space and time and relate back and forth on a personal basis as you pray FOR EACH OTHER.
There are many references in the Bible for this.
However, saints in Heaven are not omniscient/omnipresent; those are qualities of divinity. Catholics ascribe these qualities to saints in Heaven, but these attributes belong only to God.
Heaven also has one King and one Judge... and yet:
1 Corinthians 6:3 Know ye not that we shall judge angels? how much more things that pertain to this life?Certainly, we will be more than we are.