I've seen these files in mods that I've taken apart, was able to open them in gff editor only. What are these files used for?

I've seen these files in mods that I've taken apart, was able to open them in gff editor only. What are these files used for?

UTE files are Encounter templates. Encounters are a special type of trigger that maintains a leveled list of creatures to spawn when the player trips it. You can specify the minimum and maximum number of creatures to spawn, and if the encounter can only be triggered once or multiple times (and how long the cooldown period between each "respawn" should be).

You specify the intended encounter difficulty and the game will calculate what creatures from the list are appropriate by taking their CR and the player's level into account, randomly spawning creatures from those available. You can also set one or several spawn points where the creatures will appear and the game will automatically pick the one that's farthest away from the player so they won't spawn on top of you, which is handy if the trigger area is big and the player can enter it from several directions. (Spawn points are set for each instance in the EncounterList in the GIT file and not in the UTE template directly though.)

UTE templates are in the standard GFF format so you should be able to edit them with k-gff.

..You can also set one or several spawn points where the creatures will appear and the game will automatically pick the one that's farthest away from the player so they won't spawn on top of you, which is handy if the trigger area is big and the player can enter it from several directions. (Spawn points are set for each instance in the EncounterList in the GIT file and not in the UTE template directly though.)
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You have to add the spawn points or the game will slow to a crawl until all the creatures are spawned. I don't know if this is also true if you are only spawning one creature but that was my experience with the Jedi Temple mod.

Also you can manipulate spawn points in KT's Module Editor but it won't create them. You have to manually add them to the *.git file using a GFF editor.