Can the Manual HP entry be made easier? I know it’s just math, but the way it’s set up on DnDBeyond makes me avoid using it. Like the set up to manage health can be similar, but another box that you type how much you rolled, and it adds it  to your total? Maybe a history log of it as well? It’s just an idea, but it would make it a lot easier on the player. 

I'd love to see this too.  None of my players will use it.

A VERY simple fix would be to have a box for each level's rolled HP.

Level five character sees five boxes. They level up to six, there's now a sixth box that's empty - potentially with the little exclamation point warning on the manage HP button that appears on the character creator whenever you have something that's not filled out (like when you hit level four and haven't picked your ASI yet).

With the current system it's very easy for players, especially newer ones, to just completely forget to plug their new number in because they're focused on the other fun things they get each level, and even if a player does remember, if they roll low once or twice and the number seems lower than it 'should' be, now they're second guessing wondering if they forgot to put it in for a level. Am I saying this happened to me and my paladin? No, not at all...

As it is, I tell all of my players to just use fixed because effectively right now it's not reliable.