Much like you can choose what types of quests you want to see with a setting in your questlog there should be an option to add quests you do not want to see or do to a block list. This would clear up questlog space and make it easier to see if an NPC is giving out new quests. An example is the Earring, Ring and Necklace of Magical Power quests from the Black Spirit that is good for new players but once you have acquired better accessories these quests will either take up space in your questlog or bug you every time you visit Calpheon territory. One way would be to have a button in your quest log so you first have to accept the quest before blocking it. Once you select the quest and click block you get a message saying the quest will be removed from your questlog and not show up at the NPC. And if you want to do the quest again you will have to remove it from the block list and re-take it from the NPC.