(Note: I am a console player, so I can't use add-ons, but I suspect that even PC folks would appreciate these changes)!
In order of priority:
1. Guild Trader Search: Create a toggle/dropdown to enable us to search only for unknown motifs, furnishing plans, recipes, and containers/collectables. 99% of the time I only want to see the motifs/plans/recipes/style pages that I don't already know.
2. Crafting stations: Allow us to search, sort, and filter crafting plans in the crafting menu of crafting stations (i.e., sort alphabetically rather than by category; search for all plans with the word "bed" in the name, etc). While you're at it, please do the same for provisioning recipes.
3. Eidetic memory: Add furnishing plans to Eidetic Memory, so we can see which furnishing plans we know without having to go to a crafting station, and also which plans we are still missing.
4. Master crafter writs: Add a visual indicator (text color, or additional text) to writs when I don't have the skill level, research traits, or - most important - the motif to complete it ("You do not meet the requirements to complete this writ"). Even better if you can filter searches on guild traders to show only those master writs you can complete, similar to #1 above.
5. Give console players the ability to mark items as junk (or to sell) consistent with the base PC game.
6. Make treasure maps, style pages, and containers stackable and bankable in both personal and guild banks.
7. Motifs: Add an indicator of whether I know the corresponding style (i.e., I know the motif on an alt).
8. Update Keen Eye: Treasure Chests to include treasure map sites (treasure dig sites). Those freaking mounds are impossible to see in certain terrain, and we console folks can't just turn off the grass to make it easier.