Ever wanted to know just why the "Stealth Suit" ain't stealth? Is there no way to avoid direct confrontation? What are those silenced weapons and Silence spell good for? Weren't shadowrunners supposed to run in the shadows? Stealth mechanics were left kind of orphaned in the trilogy, but I created a short UGC scenario for Dragonfall that's both a tutorial for content creators and fun to play. No triggers were used to create stealth. And yes, you get a stealth suit that actually works.
Last year I waded a bit through the SRR code (Assembly-CSharp.dll) with dnSpy and came across the "Stealth Test" in the ShadowrunAI script and studied it to see what the HBS guys actually coded regarding stealth.
The stealth test is, simply put, the beholder's awareness minus 4X the target's cover bonus and 5X target's stealth skill. If the result is greater than zero, the beholder becomes aware of the target. Cover bonus is 3 for heavy, 2 for medium, 1 for light and 0 in the open. So the target could have up to 12 (4 x 3) bonus from cover.
The stealth SKILL does exist in the game code, but it's default 0 for all characters. It didn't make it to the final version of the game, so you can't spend karma on it or change it in the Character Editor or Trigger Editor. However, you can do so via items (outfits, cyberware etc) for your UGC.
Now, the other side of the equation. The default awareness for NPCs in the vanilla campaigns is 75, which is much bigger than the max heavy cover stealth bonus 12. That basically killed stealth in the vanilla campaigns, making them very combat-oriented, and the options to avoid combat were usually dialog-related.
So, can new user-generated campaigns or the vanilla campaigns be modified to use these mechanics? Yes, by lowering NPC awareness to 12 or below (I suggest 7) and giving more options to the player rather than walking into rooms full of guards facing the door. Of course, modified vanilla campaigns would still need to be published as UGC. (Be welcome to do it)
When building your UGC set the guard's awareness to:
11 if only heavy cover will hide shadowrunners from him.
7 if medium and heavy cover will hide shadowrunners from him.
3 if all three types of cover will hide shadowrunners from him.
With zero awareness he won't see shadowrunners at all.
With the guards' awareness set to 7, things get quite interesting. In the stealth test the sneaky shadowrunner's stealth and cover are constantly matched against the enemy NPC's awareness. If the enemy is in high alert, he automatically spots the intruder. The shadowrunner should keep behind medium or heavy cover to be hidden from an enemy, and not get flanked, of course. Also, hostiles will detect him if he/she walks too close behind their backs.
This basically answers the questions related to sight. In the UGC I also cover the issue of noise, which is simpler. Get it, play it and, if you like the Shadowrun Editor, use this knowledge.