The rare chest appears in the the Chest and Ammo Gallery randomly when copy and pasting the common chest - moving the chest however can change it into a common chest :
Fortnite Creative News on Twitter: "The Primitive Shape Gallery is now available! #Fortnite #FortniteCreative https://t.co/RYjR4ocRxT" / Twitter
My concept for a Custom Lootpool UI in Fortnite Creative! You can customize every chest type in the game. Set 3 levels of random loot. With each layer, you can customize the
All Holo Chest locations in Fortnite Chapter 4 Season 2
Chest and Ammo Gallery | Fortnite Wiki | Fandom
Chest and Ammo Gallery Devices | Epic Developer Community