How can I make two cells edit and display the same information in Numbers? I would like two cells to contain the same information, if I modify one the other should modify also.

I was using the Concatenate function to make "slave" cells that pull data from a "source" cell but I have to travel back to the source cell and modify it there. Are there other ways to do this?
You can't make 2 cells which content would be synchronised from each other.

To define b1=$a$1 and a1=$b$1 would create a loop of cross references.

This graph of dependency would be a cycle.

On the other hand you van make 2 cells depend on a common source:

a2=$a$1 and b2=$a$1.

This graph of dependency is a tree.