I would like to have a filter for quests that are part of a quest line that doesn't start in my current zone. I'm going for quest completion, zone by zone, and it would be more useful if I could see what quests I can actually get without having to go somewhere else.

In which version of ATT? Classic or Retail?

It might be useful for both versions, but I only play retail.

Hmmm this is a pretty niche type of request for filtering... Something that changes how it works based on what zone you are currently in? Mmm I don't know about that being added.

But anyway to try and address your issue in an alternative way, ATT is capable of plotting waypoint for multiple things at once (with reliance on the addon TomTom) and will only plot quests if their current pre-requisite quests have been met. This being the case you should be able to alt-right click on the Quests category within a given zone and see only the waypoints corresponding to currently-available quests in the current zone. Pick them up, complete them, and repeat plotting waypoints until there are no waypoints in the current zone.

There will likely still be quests in the minilist due to some nuance of pushing quests into zones simply if they have a requirement in that zone, but that process should help your focus of one zone at a time, for the most part.

Thanks for the quick replies!
I keep the mini list up all the time, and it shows the items of the current zone, I was hoping that it wouldn't be too different of a filter on top of that.
Edit: However, I understand if this is not within the goals of the addon.

Yea, going to close this for now since having a 'Location' filter doesn't currently align with the way ATT uses filtering. Maybe if there's ever a separation of Minilist filtering from Overall filtering this could be a thing to look into then.