Asepite really missing Smudge-like capability to create custom-shaped gradients and interesting backgrounds. Jumble tool does only reorder/mixing of colors and miss offset/nudge capability. I suggest to add Nudge power to Jumble tool (fading to zero over distance). Or to add separate Smudge tool…
To create interesting gradients I had to go super low-res, mix gradients with Jumble tool (which size limited to 64) and then gradually resize to higher res 2x with refining using Jumble tool each time. It was tedious.