Minecraft Carry On Mod not working?

This mod has only one function and that is that you can carry animals and boxes directly in your hand, why doesn't that work?

Are you pressing the wrong key?

Some mod items, including chests from other mods, do not work.

With modpacks, the config can also be adjusted so that you can no longer carry everything.

It worked and so with mobs from other mods such as Ice and Fire

i have it on standard and it doesn't seem to do anything, do i need to have something written down in the whitelist/blacklist area, sorry it's been a while since I've used mods

for me it carries some mobs sideways

what button i need to press?

how does this even work.