It's extremely useful when dealing with a dedicated "functions" event sheet, multiple event sheets at once, or a combination of both. Sometimes you want to keep relevant functions in a group, but if you want to add another action (say, when you create a new function parameter), you may have to switch event sheets (which is an instant breaking of your work flow) and then hunt down the function itself. Given the awesome new searching features in C3, it would be great if there were a clickable link or some way to instant pull up a given function's "On call" event so that we can easily work with both the "Call function" and "On Call" events together. Of course, you also have to take into account have multiples "Call functions" for the same function and multiple "On Calls" as well, so you would need to be able to pull up all events involving a specific "On Call."
C3 r54 adds support for 'Go to function'! There's also 'Find all references' for functions which can comprehensively list everywhere it is used.