When summoning a horse with a custom entity as a rider, the custom entity does not spawn.

When using commands such as "/summon horse ~ ~ ~ {Passengers:[{custom_mod:custom entity}]}" in procedures and in-game the custom entity does not spawn. I have double checked, and tripled checked but while the command is correct, it does not actually summon the custom entity. Any solutions/alternatives would be great.

Version = 1.18.2

MCreator version = 2022.1