I was told to put this here, but I think a nice way to keep the quest menu tidy without it being overbearing on quest creators is to have a section at the bottom of the quest list for completed quests that's collapsable and has the quests darkened/greyed out. I believe this would stop the quest list from getting too large which would make it feel more manageable and easier at a glance for players figuring out what they need to do next.