Uploaded a new version with a few minor edits. Uses dialogue from version 3b.

My comments:

; Unfortunately only works if chest has not been emptied before
if that's a concern I recall there's a hacky fix for that, maybe it's putting a no-model light object in the chest? something so it can't become empty

This is not very important. It would not be any logical move to loot the chest if choosing to proceed along this path.

; check if ANY spoiled potion is in the chest
if the script will need to be updated for any future generic MW spoiled potions that would be worth noting somewhere... don't know where, probably a couple other scripts like that in the mod

This is a bit of an edge case. The player receives one spoiled potion from the questgiver which they are supposed to put in the chest. I have just implemented it this way in case the player happens to have another spoiled potion in their inventory, so they would not need to be confused on which one to pick. It would however make sense to update the script if more variants are added, since later all spoiled potions in that chest are supposed to be confiscated, so it would be a bit illogical if some of them are missed. But again, edge case.

if ( TR_m4_Tilara_Danar->OnDeath )
if the NPC exists outside of this quest I'd consider making a script on her even if it's just with a comment for any later use to not try OnDeath on her without changing this script, because that function can only work in one script?

It would break this quest if some other quest would task the player to kill her, so I hope that would never happen. I tried to avoid giving Tilara a unique script since I had so many already, but I agree that this should be documented, in case another quest needs this check (e.g. for similar reasons as this one).

elseif ( GameHour >= ( frameHour + 1 ) ) ; player rested
it seems like the normal condition for this scene to start is player changing cells (like entering "Andothren, Nevusa Falen: Alchemist") so I guess the resting checks here at sceneState 0 are just in case she'd been commanded into that cell already?

It is just an alternative way to trigger the scene to start, in case the player would rather stay in the cell. Rats suggested that she could be triggered to leave from the dialogue instead, which would make this redundant. While I don't think that would be a good idea, making her leave as soon as closing the dialogue window would probably be the best option, possibly along with an "Open Door" sound (I was not aware how close she was to the door when writing the script).

if ( timer > 20 ) ; wander for at least 20 seconds upon entering
            TR_m4_Tilara_Danar->AITravel 4092 3885 15439
            TR_m4_Tilara_Danar->SetHello 0
you may want to do that SetHello 0 earlier when she starts to wander or these 20 seconds could be spent staring at the player (maybe even before the AIActivate? depends on which engine you use in vanilla the waiting time after voicegreets is very long, in openmw iirc that was replaced with a much shorter anim)

20 seconds is pretty long. I tested this on the Vanilla engine, and the greeting interrupting the investigation was not a big concern. You also have to keep in mind that she is required to stay in the room for at least 1.5 hours before triggering the next state, so for most players it would rather be a few minutes than 20 seconds (you have the option to rest in case you think it takes too long).

should add one more argument in AITravel lines like these to prevent the sequence from breaking on player resting, one thing it does is some special AI failure resetting (something not relevant in cells that should have pathgrids like these) but also it makes sure GetAIPackageDone does get detected if resting happens - probably not necessary in MOST of this script since it already handles resting if scene >2 <7, but at scene 8-10 there's also something that depends on AITravel GetAIPackageDone. your other scripts with similar AITravel GetAIPackageDone already handle player resting in all cases it seems

Unless you kill Nevusa, player controls are disabled during this episode, so this is not of any concern. If you do kill Nevusa, sceneState will automatically be set to 10 if you leave the cell, causing Tilara to teleport anyway.

if ( timePassed <= 3 )
                PositionCell 4153.268 4940.933 15061 10800 "Andothren, Fauler's Philters"
no AIWander after this PositionCell? assume you know why since your other scripts do it

The guard is still disabled at this point, and if reentering the cell, he will get teleported here again, so I don't think this is of any concern. I tested to rest after this triggered, and it worked fine, but I'm not sure if I also tested to leave and reenter several times, which would be the only thing I could think of that could cause any problem.

lseif ( sceneState == 3 )
...
            if ( GetDeadCount "TR_m4_Hemmette_Fauler" == 0 )
if that NPC is dead it looks like nothing more happens on this script's side so this would remain at sceneState = 3, then you'd want to do something to put a stop to this check because GetDeadCount every frame while in range can cripple some players game, it's a special vanilla engine issue only with the GetDeadCount function if there are lots of dead IDs in a save file

This is really an edge case, which would only trigger if you have killed Hemmette during the short interval between when the guard "enters" the room and he is supposed to arrest Hemmette; otherwise it will only trigger once (sceneState is changed in the dialogue). I never tested this actually. On second thought, this check is probably redundant, since killing Hemmette will change the journal stage, preventing the script from reaching this line anyway.

Set TR_m4_Ando_AlchemistsTimer.timerSet to 0
    StartScript "TR_m4_Ando_AlchemistsTimer"

a note for when this gets tested in openmw, there might have been issue with setting scripts local variables base records like that? if someone reports it doesn't work in openmw yet maybe try swapping the order of these lines, same in script TR_m4_NPC_Nevusa_Falen and in some dialogue results

I have only tested this on the Vanilla engine, and there it worked. This could be the reason why Rats had problems with the TR_m4_Ando_TilaraInvest script, though, since I have done something similar there.

 if ( GetDistance Player <= 256 )
        if ( GetDeadCount "TR_m4_Nevusa_Falen" == 0 )
same comment about GetDeadCount as in script TR_m4_NPC_FaulerGuard

Here the check needs to be done unfortunately, and no, I didn't test it here either. I think I should add else Set sceneState to 5 here, because otherwise this could potentially break the quest. There is anyway already such a check in the dialogue, so this is really an edge case.

Since I got some interest in playtesting this, I have now made a few changes following Rot's comments. I have fixed the following:

• Tilara Danar now leaves for the investigation immediately after telling the player.
• Tilara Danar has got her own script in order to control her OnDeath behaviour.
• Local variables in global scripts are no longer set before running them (I hope I didn't miss any).
• The GetDeadCount issues have been resolved by either removing them or replaced with a GetHealth check. In the latter case, sceneState is automatically changed.

Thanks for testing! I'll fix the typo, no worries. Regarding your other remark, I can only say to you'll have to edit the esp according to the merge notes. For this to work properly, you'll have to remove all the indicated objects.