Would be nice to have for mods that add "leathers" comparable to regular leather.

It’s in the Neo side already.
https://github.com/neoforged/NeoForge/blob/c36a5ea78012784398ef93ebf1faf0a6e6913c72/src/main/java/net/neoforged/neoforge/common/data/internal/NeoForgeItemTagsProvider.java#L135

Forgot about fabric side but seems good for someone to PR to add it. I guess I skipped it over due to only finding one mod using a similar tag on fabric. But if more are gonna use it, let’s add it to fabric side to match neo

would be c:leathers

As per the field name, it should be leathers. I’ll make issue report to Neo as nouns should be plural

It’s in the Neo side already.
https://github.com/neoforged/NeoForge/blob/c36a5ea78012784398ef93ebf1faf0a6e6913c72/src/main/java/net/neoforged/neoforge/common/data/internal/NeoForgeItemTagsProvider.java#L135

Forgot about fabric side but seems good for someone to PR to add it. I guess I skipped it over due to only finding one mod using a similar tag on fabric. But if more are gonna use it, let’s add it to fabric side to match neo

would be c:leathers

It's c:leather in neo