TL;DR
Replace the signal value slider with value shortcuts for "Stack Size" and "Rocket Capacity", possibly along with multipliers like "x2" and "x10".Why?
I've observed that the signal value slider rarely ever serves any useful purpose since whenever I'm bothering to set specific signal values, the slider is just too inaccurate to be of any use. I understand that the purpose of the slider is to enable a quick mouse-only interface, but the inherent inaccuracy of a slider means that in nearly 1000 hours of gameplay time, I've almost never, ever used it. Previously, I hadn't felt the need for UI improvements of the sort because I simply wasn't relying as much on circuits. The amazing new improvements in 2.0 have made the circuit network a lot more accessible, but I feel like the signal selection UI now needs some updates.What?
A minimal mouse-only interface for setting signal values (to avoid using the keyboard) can be achieved by providing shortcuts that directly fill in the default (1) with commonly used / logical values such as the selected signal's stack size and rocket capacity. The inclusion of some simple modifiers that change the currently filled value in-place, e.g. multiply by 2, 10, 100, +1x. +2x etc. would enable signal value selection to become a lot simpler. Of course, for more complex changes, a player can always type it in, but this should already cover 80-90% of all cases.A more concrete example: say I want to set a signal to 10 times the rocket capacity of something. The workflow with the proposed UI would then be:
1. Select the signal
2. Select the rocket capacity shortcut
3. Click the 10x button
4. Confirm the signal value by pressing the green tickmark button.
Alternative example: say I want to set a signal value to simply 4, the workflow could then be:
1. Select the signal
2. Click the 2x button twice (double the default value 1 twice)
3. Confirm the signal value by pressing the green tickmark button
Edit: I've added a rough sketch of the idea: