If a character is added to two parties, they cannot see the quests from both parties, only the last one created. In the campaign we are playing, the party consists of members of sub-factions. While the group as a whole receives quests, each sub-faction also assigns tasks. I originally had the idea of creating a party for each sub-faction with only the characters of the main party that belong to it, and creating the sub-factions quests under that party, so that they only see the main party and sub-faction quests that are relevant to their character. Once the character is added to the second party, they can only see the sub-faction quests, and no longer see the main party quests. I originally thought this would be a great way to differentiate who assigned the quests since the party name appears right under the quest title.
I use a GM account to create the parties and quests, and a seperate "testing account" to create the character and view the quests under.