Are there any good addons for managing transmog runs? Like a checklist of each legacy raid/dungeon for the week, and what I have and haven’t unlocked?
All the Things
It’s big, but its what you’re looking for.
Based on @Letholas answer, I’m not 100% sure what you’re looking for.
But I used an addon called “Executive Assistant” that lets you track all your alts, what they’ve done, etc etc.
It requires a lot of setup and I didn’t find it very intuitive. But once you get the hang of it (15-20mins?), it did EXACTLY what I wanted, where I have yet to find a similar solution anywhere.
A lot of people will say “but you can just log in your alts and see much of the info EA tells you.” Right, but once you have 10+ alts, you’re wasting time doing that, when you can just look on your main and know what you need to do; remind you of where you left off, etc.
It’s the kind of addon where, if you need it… you NEED IT!
Hope this helps. 
SavedInstances provides a single-pane view of the instances your alts have ran.
I have that installed, but it’s kind of overwhelming and hard to follow. I almost want a TomTom route to follow, and once I’ve collected everything it will skip an instance in my route.
Second vote for All The Things.
It tells you what you need from any place in game. Recipes (including who can learn them), transmogs by boss and difficulty, pets, mounts, quests, everything. ALL THE THINGS.
Very very fantastic. It also shows you at a glance if you already did a lockout for the day/week.
For the rest of it, I use spreadsheets. Just keep it simple and let All the Things do the work.
| CharName | CharName | CharName | |
|---|---|---|---|
| Dungeon 1 | . | . | . |
| Dungeon 2 | . | . | . |
| Dungeon 3 | . | . | . |
| Raid 1 | . | . | . |
| Raid 2 | . | . | . |
| Raid 3 | . | . | . |
| Zone 1 | . | . | . |
| Island Exped. | . | . | . |
| Timeless Aisle | . | . | . |
| Isle of Giants | . | . | . |
| ETC | . | . | . |
So you can just check off those each day or week. ATT will tell you what you need from each place when you get there for each char.
You have your raid lockout for what youve done
Appearance tab for what is still available.
I usually throw in excel the item to track by specific item
Is there an easy to way use All The Things + TomTom to route me to the next instance I click on?
I am not familiar with putting in a route into TomTom.
I know All The Things does not do it automatically or anything. I has a mini window telling you everything in the zone, or dungeon/raid you need to get but you can customize that.
My personal suggestion is to pick an Expansion and focus on that until you get that one done for whatever you wanted to collect. That way you are familiar with the routes.
Mira- your spreadsheet there… is what Executive Assistant does. 
Also- there was something I forget what it was, but it was EXACTLY what @Muvi is asking for.
It showed everything you were missing, and suggested a route that would let you try and collect all the things you were missing…
AHHHH It’s: Simple Armory. Which itself is super cool to see what you’ve collected. But you then tick the checkbox for “show planner” and it’ll tell you how to best go about collecting the stuff you’re missing. It’s SUPER COOL!
`https://simplearmory.com
ATT is great, but a massive resource hog
MogIt and Can I Mog It… mostly Can I Mog It. Just adds a tag to items that tells you if you’ve learned, can/cannot learn, or have learned them from another item. Saved me from accidentally equipping items below my armour class.
Works in adv guide ui. so you can see if the stuff bosses drop have been learned.
That is awesome! I will definitely check this out. Thanks
I can also recomend ATT (All The Things) but as others have said its resource heavy, but if it doesnt cause any issues for you its nice since it does lots of things, and for your case it’ll show what appearnces you still can get.
Though i’d check this out as well
Another upvote for Can I mog It? It’s one of those must-haves for collectors.
Are you wanting an auto route to the next instance? Cause I don’t know if that’s possible but I just click the instance icon on the map and TomTom gives me a waypoint arrow to it. Seems to only work in some areas, though.
This is the best answer. Allthethings is far too bloated. Just use this. It integrates into the base UI and provides a simple, at a glance overview of what you have and haven’t done.
Also use in conjunction with Canimogit to immediately tell you what you have and don’t have from boss loot tables.