The only monsters causing Jumpscares in Abiotic Factor so far are the Leyak and the Reaper. The first one spawns nearly everywhere and haunts the player while the second one only spawns in the Security Sector at given spawn points, patrols its area, and then despawns to spawn again at the nearest spawn point to the player after around 30 seconds. I hate Jumpscares, therefore this mod should be used if you hate them as well! It warns when they spawn and additionally for the Reaper also informs that it despawned.
This is a mod relying on UE4SS for Abiotic Factor and was heavely inspired by the LeyakNoMore mod that is way more customizable but also despawns the Leyak and drops its essence. I tried to mimic it at first as well to be a complementary (like ReaperNoMore) and only despawn the Reaper and drop its essence but this was not straightforward and I am not really proficient with Unreal Engine and FModel.
This mod relied on the UE4SS configuration for Abiotic Factor, and FModel for checking out the Mapping Files for Modding Abiotic Factor. I personally like to use Visual Studio Code for the actual Lua development.