First: Dialog options do not show up ingame directly, after you activated the plugin and loaded the game. You have to save inside the instance, the npc is located and load the game after that, to see the new dialog. Someone in the german Scharesoft-Forums told me that this is allready a known bug.
The second problem I encountered is with creating Quest Aliases in the Quest Alias Tab. If you do so, no dialoge option will show up ingame ever. Doesn't matter how often you save and load the game.
For any NPC-Character this can be fixed by selecting the NPCs Alias as "Force Into Alias When Filled" but this doesn't work for Items created in another alias. Besides forcing anything as explained before is no viable solution.
What I'd like to know is, if there is any workaround for this issue or if anyone else has encountered the same problem, so I can be sure, that its truely a Creation Kit Bug.