2da Missing Items
There are 6 items you can re-enable since they reflect valid saving throws (The game actively has for usual effects and script functions). These are Traps, Spells, Law, Chaos, Good and Evil.
Note Backstab and Illusion will do nothing.
The 2da rows are hardcoded but these are helpfully already labelled. Not having a TLK reference means it won't load it properly. To fix it use this example fixed file using existing valid TLK entries.
2da Hardcoded Limitations
Even if more entries are added the engine will essentially ignore them. If you add new rows they might appear and be selectable but they'd only do something if there were scripted elements. So adding a saving throw vs. "Fairy Spells" you'd have to manually code it in somehow (or use NWNX perhaps) if the game loads it at all.
To be honest adding a new item property in NWN:EE is a lot easier with ItemPropertyCustom (if scripted) or in the toolset, and more reliable/safer, and you could even name it the same way for the user.
It is a shame this list doesn't match the default SAVING_THROW_TYPE_* constants allowing manual additions (if the effects to increase/decrease and the saving throw functions also accepted the increased numbers).