To quickly find the defining function from anywhere inside a script, right-click the function, and choose “Go to Definition”.
ISESteroids selects the editor that defines this function, and brings the function into view. This works across multiple open editors. It even works for Untitled documents and documents you have closed meanwhile.
“Go to Definition” will not yield a result if the function is not defined in memory. This is by nature. ISESteroids cannot know where a function definition lives until the function has been defined in memory.