TL;DREnable multiple combinator steps to take place in a single unit, for ease of programming/readability/portability/space-saving.
WhatA replacement UI for combinators (potentially merging Arithmetic/Decider combinators into a single entity) similar to the Train Stop UI.
The below is an example not a fully tire-kicked design.
Why ?The combinator system is one of the most powerful things about Factorio, but it is not without its foibles.
There are many suggestion threads on various things that people would like to see changed, with one of the big ones being readability and scalability. One function takes two squares. Rearranging a "code block" can mean moving a whole array of combinators around and remembering which input goes where. It can often be easier to design things from scratch than to try to modify existing blueprints unless you were extremely well organised at the start.
There are some mods that try to add some programming to the combinators, such as fCPU, but while they're powerful you do have to learn something new and outside the normal factorio system.
This kind of thing would use existing Factorio UI elements seen in the train stop UI, such as the AND/OR buttons, and enable multiple combinator steps to happen in one device, simplifying layouts and enabling a more configurable "building block" approach to contraptions.