TL;DR
The ability to select areas on the map to control certain behaviors for various mechanics.What ?
Selecting areas on the map to create new 'zones', to then selectively adjust how your factory behaves in those areas. Bot pathing and changing how alerts work are the primary use cases for such a feature, but I'm sure more uses exist.The following image is a quick edit I made of an old factory screenshot of mine, to visualize how the proposed mechanic would be employed. The red areas are zones designated 'No-Fly', where bots are not permitted to traverse through. I've drawn them such that bots will avoid biters and areas without roboports.
The dark blue areas designate a custom alert zone. In this instance, I'd disable alerts appearing for turrets engaging and most structures being damaged at my perimeter walls (namely walls and turrets). Thus, the alerts in the bottom of my screen wouldn't be clogged with unimportant alerts for a wall being gnawed on or a turret dealing with a stray biter. However, I'd still be alerted if something actually got destroyed! I'd also still get alerts if somehow biters snuck into my base and started gnawing at any of my leftover interior defenses, so I could take care of that immediately.
The following image is a mockup of how the custom zone UI might look like. I just stitched screenshots together from various UIs and icons (Also ignore the modded icons!) It's rudimentary, but the gist is that you'd give a zone a name and open its configuration menu, to then select buildings and corresponding alerts, and whether you want the selected alerts to never show up, or *only* the selected alerts to show up. Zones with the same name will share the same configuration, even if they're not connected.
In this example, turret-firing and building-damage alerts won't show up at all, leaving only building-destroyed, no-repair-packs, no-material-for-construction, no-storage, and not-enough-robot alerts showing up.
The light blue zones are areas where bots will prefer to path through. I've drawn them such that bots flying through there will always be near a roboport. (Granted with the robot AI changes detailed in FFF #374 this won't be as important, but still!)
Why ?
There are certain behaviors to the game that you have little to no control over, which range from a minor inconvenience to annoying to somewhat problematic. The ability to adjust how your factory behaves in specific areas would be quite helpful for alleviating some of these issues.This is admittedly... not a terribly big deal? At least the use cases I've presented. However, creating zones within your factory for behavior control seems like a sensible addition. For instance, City: Skylines has a very similar mechanic, and it's vital for ensuring your city develops how you want it to! I'm also sure modders alone could find uses for this mechanic if it had enough flexibility to apply to more than just bots and alerts.
The main inspiration for this was actually DoshDoshington's first Rampant video! Specifically, this moment where he notes "If only there was a way to make alerts only sound for things you actually care about." https://youtu.be/FLbJMBM7QnM?si=82oB-OWg_sQthZjV&t=734