It seems that there's a chest texture inside the file of the game for horses, but it doesn't seem actually functional. it should allow you to put stuff inside a horse chest. I was thinking do pocket an equip button could show up, and on Windows 10 you could right click to put the chest on.
MCPE-20183
No chest for horses.
Resolved
Works As Intended
0
This is working as intended. Chests can only be put on Donkeys and mules, not horses.