Would it be difficult to add some stuff under the hood to make it so that when you spend hit dice on a short rest, it has a box underneath to put in what you rolled so it can heal you that amount?

You can do that anyway from health field. Type in what you rolled and click heal

Why is it when I suggest a small quality of life improvement someone always comes in and goes either "this idea has this round about way to do it anyway" or "this doesn't affect combat so no"?

It's not round about, it's literally what you asked; the ability to enter what you rolled and heal by that much...

I was saying on the same window where you can tick off the hit dice on short rest, to help simplify things for players. As in it offers a box on the short rest window you type the numbers into and it adds it as healing when you confirm the short rest.

Doesn't that already happen? Or do you mean for it to be that when you click off the box in the short rest window, there would be a small spot to put a number into? Because I can see the usefulness to that. Basically type in a number, check the box, and it adds that number to your current health and 'uses' that dice. It definitely would have removed the confusion I felt when I was trying to figure out how to use my hit dice for short rests when I first started using this site.

Ah, I misunderstood what you were asking. Yeah, I can see the usefulness of having the HP management options in the short rest menu.

 That would be slightly useful, but I would rather they prioritize work on other features.