Unless I am missing a hidden tag or config, I wish there was a way to add other mobs to be blocked by the enchanted ash.

Currently, other undead mobs from other mods such as Born in Chaos can pass the ash despite being undead.

At the moment it uses a vanilla flag for undead entities

mcreator probably doesn't use this
(in 1.21 this check wil use a mob tag in vanilla but for 1.20 other mods would need to set the mob type to MobType.UNDEAD)