I don't know if you play a mage ureself but from following bluedot's SC/Ele rotation (without building storm) your Forked/Thunderbolt cast should end just where the red bar starts perhaps you could add a marker for the recast (I know you tried doing this with the white and red segment of the bar.
But perhaps giving people like a white marker in the Shape of a | would make it even easier to understand when to recast Forked/Thunder I'll try screenshotting it with the addon in action and then mspaint the marker on there so you can picture what I'm trying to say if it isn't that obvious
This is just an idea ofcourse.