have you thought about added a Related Quests link to the lower Collections that would list the higher collections they are assicated with.
Achievement: Nothing Left to Fear
•Achievement: Chasing Cazic
•Achievement: Cleaning Up Cazic
Achievement: Chasing Cazic
•Achievement: At the Source
•Achievement: Chilling with the Giants
•Achievement: Down to the Last Dwarf
•Achievement: Heralds of War
has to realated quests that are below it. but when I open the lower quests their is not a link showing its part of a higher quest.