Currently, if you are looking at the main map and use the Show Active Quests feature, any quests on a different map show up in red.

What I propose is that the entrance to the area/map that the quest is in should glow green when you hover over it (for example, I am working on Flowers for Lucy so when I hover over that quest, it highlights the Buried Pyramid square on the map).

This would be especially useful for Giant and Share the Wealth quests as they can show up anywhere.

I also suggested once in a help request, that on any Quests in ones Quest log, those that are completed but not turned in yet be shown in a different color in the Quest Log from thoae that are not completed yet.

For example, if you do EVERY repeatable Quest every time you can and start them all at one time, as you finish each one there is no way to know from just looking at the Quest Log which ones are done and which are not. You actually have to click each and every one of the 45+ Quests in the Quest Log to see which are donew and which are not.
I don't exactly do this, but when I'm not Maxed Out I slowly work on all the extra Repeatable Quests that I doin't normally do and then hold off on turning them in when the next Level Cap increase happens. And I might have a few that are not quite done yet, knowing which is which is a task.