How do you guys determine which NPC slot is discarded when an adversary is defeated?

Randomly determine?

Remove them from the Front of the que?

Remove from the back of the que?

Keep record who who rolled each slot, and remove that one, even though they may not be acting in that slot?

Obviously, the players would prefer you remove the ones at the front of the que, so they have more actions before their foes, and the reverse would be true for the adversary.

How do you deal with it?

I remove from the end. NPCs need some loving too!

My group's never used a steadfast rule, the GM picks one that makes sense and we move on. You can kinda inform it by the initial rolls if you kept a record.

I don't worry about removing slots, I just let the NPCs act when an NPC slot comes up and if there aren't any NPCs left to act in a slot, I skip it.

I remove from the end. NPCs need some loving too!

This! The bad guys have such a hard time of it anyway, even a strong and well built nemesis is outgunned by a PC team, that I have no problem giving them as much a leg up as I can.

Last one, same as if a PC drops out of combat.

Pile on vote...last one as well.

I wipe out the last initiative slot as well. I have had players in the past try to convince me to take out the "slot they had rolled". I find this to be too cumbersome to try to track. I also don't track which PC rolled which slot. If I had a PC go down in a fight, I would take out the the last slot on their initiative count as well.

Is there any benefit to removing the slot rather than just letting it exist unused?

Does anyone also do the same for PCs? What happens if they regain consciousness?

For me, it depends on the type of enemy defeated. Minion (whole group): end, Rival: middle, Nemesis: beginning.

If a PC falls, I remove the last slot. If they make it back, I have them re-roll and add that to the other slots.

Is there any benefit to removing the slot rather than just letting it exist unused?

Does anyone also do the same for PCs? What happens if they regain consciousness?

There's no mechanic for holding actions, so having more slots than actors creates more options to act later in the order. I think an extra slot could get confusing, too, when trying to figure out who hasn't gone in a round. To me, an unused slot is the same as removing a slot. Jedi Fenis' beginning, middle, end approach works. I'm just too lazy and take out the last slot, since after the first round everything gets pretty fluid anyways.

I don't actually remove a slot. Simply let the NPCs act when the slots come up. If there are no NPCs available to act in the round, the slot is skipped.

We remove the slot that the character who fell unconscious was using in the round it left combat.

This has never caused problems but the flow of combat is different with players choosing which slot to act in each round.

For the most part, unless they are setting up a coordinated effort, the players tend to pick a slot and stick with it.

Why do people want to remove slots? There is nothing in the rules for removing slots. If there is no one left to go when a slot comes up, then you skip to the next slot. This allows for people to take a later slot if they want or for new people to show up and not have to roll to see what slots they can contribute.