Found a neat extension that tracked exp in 5e. Basically it lets you know when you level up as you are assigned experience. I modified it with the creators permission. Thanks Laendra! In the option menu, you can set the exp advancement speed. fast medium slow 3.5E or off. this will also auto populate the exp needed field. best of luck!
Edit: Now supports 3.5E!
Now on Forge: https://forge.fantasygrounds.com/shop/items/703/view