How can I identify to which quest line a specific quest belongs
Solution 1:
You can tell by looking at the symbol next to the quests name when viewing it in your quest log.
The Bards College does not have a symbol of it's own, but instead uses the generic Side Quest icon.
Main Quest
Side Quests
College of Winterhold
Thieves Guild
Dark Brotherhood
The Companions
Civil War
This icon is shared between the Stormcloak and Imperial sides. It is the only asymmetrical item in this list.
Daedric Quests