It is the one you find right under ".../GOG Games/Neverwinter Nights Diamond Edition". You do not add anything. Just change the value that is already there. See attachment.

Sorry for the necro but I'm starting to lose my mind.

I have the NWN Diamond edition, clean install no external patches no nothing.

I changed the file in G:\Games\GOG\NWN Diamond where my installation is, got there via the 'manage installation>show folder' in Galaxy so I'm 100% its the right place.

I edited the value. You can see it in the screenshot attached.

I am still getting random values on levelup. It's particularly frustrating when starting new HotU campaign since I need to roll the levels for 30 minutes or modify the HP values in Leto.

Is there something I'm missing? Does this not work in singleplayer?

It should work in single player, no idea why it does not.

If you save and close the ini file after the change, then run the game, quit and open the ini file again, does it still say "Max Hit Points=1" or did it switch back to 0?

It stays 1. I can see the file timestamp is getting updated but the value is still set to 1.

What is interesting, if i completely delete the file and start a new game the new nwnplayer.ini doesn't contain the "Max Hit Points" at all so I'm wondering if it is even used right now...

Edit:

OK i found the issue.
I have installed english version of NWN, then changed it to Polish after.
Even though the galaxy client shows that the version of the game is 1.69(A) the version after language change was in fact 1.68

The update function in Galaxy did nothing so i downloaded the 1.69 Polish patch from neverwintervault - polish-nwn1-hotu-169 (i cant post links for some reason)
Now everything works as expected and i even got a new prestige class to choose... GOG - get your act together