I think there were jump sprites at one point, but they were removed because you'd have to make them for every skin, and skulltag's netcode caused them to be very buggy.
Doom Builder 2 (the level editor we use) is as close to an in game editor as we are going to ever get. It has a visual mode so you can see pretty much exactly what the level will look like in game, minus some effects like skyboxes, line horizons, and such.
They at least need to try to give people the option of making a jump sprite.
Oh, and I think I'd like to try using Doom builder. Where can I download it, and more importantly, how do I use it?