Hello,
You need to put true at the "save" param:
http://wrobot.eu/byme/doc/html/M-wManager.Wow.Helpers.NpcDB.AddNpc.htm
NpcDB.AddNpc(TheNPC, true, false);
For fightmaster:
http://wrobot.eu/byme/doc/html/M-wManager.Wow.Helpers.Taxi.TaxiList.AddOrEditForCurrentPlayer_1.htm
TaxiList.AddOrEditForCurrentPlayer(TheTaxiNode, true);