enchantencore:anchor
Anchor is an enchantment from the Enchantments Encore data pack that can be applied to saddles and harnesses. It prevents mounts from wandering when they are not being ridden by a player.
The enchantment can be obtained from Loot Sources using the Enchanting Tables, Random Loot, Traded Books, Traded Equipment and Mob Equipment tag lists.
When a mount has this enchantment applied to the saddle or harness it is wearing, its movement and flying speed are reduced to effectively prevent it from moving. Once a player mounts the entity, its movement speed returns to normal.