Since transmogrification added in WOW, some kinds of low level and unique items attract many players. BOE gears like Teebu's Blazing Longsword, Glorious Set, and Bloodscale Set are valuable, and Raid dungeons do not drop the cool weapons and Armor. Bank and backpack are fill with all kinds of equipment.
Blizzard is also feeling the passion for transmogrification, they then modified transmog in Legion and satisfied players. Let's see the new features of new transmog.
The Fabulous achievement acquired together amd The Fabulous title, requires you to collect 100 appearances of Armor, and 15 appearances of Shirt and Tabard. Gaining an achievement for transmog is amazing!
Once collected appearances, you are allowed to transmog the appearances, although you've deleted it. In which way you will get more space from bank and backpack, that is the most important point. The transmog system has the collect function that will help manage transmogrification you liked, and for you to switch at any time.
You will unlock the transmog by equipping, and unlock quest transmog to your transmog Wardrobe. 
Your transmog options will be stored as an account-wide collection. 
Blizzard added Wardrobe Tool feature to let you track your collected transmog appearances. You can see all transmogrification, as well as transmogrification you've collected.
To collect weapon enchanting appearances, you need to kill bosses from dungeons and raids in old expansions.
Alright, look the Fabulous as a new function, and to experience the charm of the wardrobe when patch released.