Ever since I first started playing ESO, I couldn't help but notice the lack of any form of experience bar. In order to see where exactly you are at, in terms of leveling, you must go to the character screen. Don't get me wrong, this is better than nothing but being able to see how much killing a certain creature raises the bar would help you know if it's even worth fighting.
I don't think this is a very hard mod. Honestly, you don't even really need to create anything new, just move the bar to a better place that's more friendly for in game use and add an option for it just like the other GUI elements you may toggle on or off. Honestly I feel like there is already something for it. If anyone knows anything or could make something like this, please let me know!