Currently you can only have one quest 'pinned' (excuse me for possible wrong terminology). Which means you can only have one purple objective indicator on the map.
I think it would be a big improvement to the game if it would be possible to 'pin' more than one quest, especially if you're doing quests that are meant for a certain area, for example; a tomb or the sewers.
I don't think there is much more to be added, that's about it. It would be cool to see what other people could add to this.