Custom code navigation

Unfortunately, you can't do that with Advanced Metadata currently. Please vote for the request: https://youtrack.jetbrains.com/issue/WI-36647

What you can do is to add @method PHPDoc blocks in every class (or their parent), like:

class Blog {
    function getBlogsRating() {
        return new DateTime();
    }
}

/**
 * @method DateTime Blog_GetBlogsRating
 */
class Invoker {

    function test() {
        $this->Blog_GetBlogsRating();
    }
}

For obvious reasons, you'll need to adjust the docblock each time you change the method itself.

As for the plugin development, you can get hints here: https://confluence.jetbrains.com/display/PhpStorm/Plugin+Development