Would be cool if there was a sky creation tool like this in Unreal Engine:
It’s called Helios SkyBuilder, and it’s basically dragging the gradient values with set markers/keys and adding coloring like you would in a 2D paint program.
If not in Unreal Engine then perhaps a 3rd party company putting it in a tool such as Substance Painter would work.
Have you looked at the Sky blueprint used in the templates?
Check out trueSKY for Unreal Engine 4
You could easily do that in the Material of the Sky, you won’t get Drag-And-Drop gradients, but you can create gradients in the material editor and plug colours into them, and there’s theoretically no limit to how many colours you can have. As it’s a material you could change them at Runtime too.
The default Sky material uses a DotProduct to generated an upward-facing mask I believe. you could either create a gradient node in HLSL for the material editor, or just tweak the existing DotProduct masks and use a few bits of math to add extra steps or tweak the gradient.
Yes I have, I like it. 
I like the day and night cycles too.
Thanks Ryan, that looks like a great product, it seems a bit pricey though and I’m not in Columbia or the UK, it’s a bit different than what I was hoping for but close.
Sky/Horizon UI for Gradient type Marker Based System
I was thinking more along the lines of a popup dialog box that would allow you to simply click on the gradient and add extra colors using drag-able markers, where you can click on a vertical gradient bar representing the horizon, thus, creating a marker and set a color for each to create varied horizons that way, just a quick little tool.
Alternative Solution:
I suppose I could just do it in a paint program and load it in via an external image or use the sky stuff that’s already in the engine like was mentioned using some chosen colors and/or using the node based method.
Thanks!