It's simply when you are in creative, the ominous Vaults and spawners are not available through the inventory.
MCPE-182628
Ominous Vaults and ominous trial spawners are absent from the creative inventory.
Resolved
Duplicate
0
Ominous trial spawner is simply a temporary block state of regular trial spawner. As for ominous vault, that is MCPE-180961.