It would be nice QoL to have additional inputs for Chemical Dispenser: 2, 3 and 4.
Chemmaster UI doesn’t have enough space for additional three but it could be widened.
Given how laggy double-pressing input buttons is even on a local server, that would simplify choosing 2, 3, 4, 7, 8, 9.
I’d implement it myself but I’ve only found the code for the UI and I don’t know how what function reads the UI.
Also, here’s a random semi-related idea I may or may not suggest:
Numpad mode. First choose a chemical, then quickly press one or two digits on the numpad.