Hi Jeff,
Here are a few options to choose from based on your preferred workflow.
Option #1
In the Dialogue Editor, you can link across conversations. Create a "hub" conversation that the NPC always starts at. Then create separate conversations for each quest, and link from the hub to the appropriate quest conversation based on the states of quests and/or variables. To add a cross-conversation link, select the originating node. In the Inspector, find the Links To: dropdown and select "(Another Conversation)".
Set the Conditions fields on the destination nodes so the Dialogue System will know which link to follow. You can also use
priority levels on nodes to make the conditions simpler.
Option #2
On your NPC, add a separate Conversation Trigger for each conversation. Set each Conversation Trigger's Condition so only one will be true at any given time.
Option #3
Register a C# function that finds your
ConversationTrigger component and sets its
conversation property (a string which is the conversation's title). Use this function in the Script field of your dialogue entry nodes.