Used to be I had two turtles equipped at all times. When I got a 3rd one, I was not able to equip it. When I removed all of them then tried to equip them, it would not let me anymore. I do not know if we cannot do that anymore or it is a bug.
The Top image being the weapon/item hotbar, the bottom being wearables. I was able to have more than one on wearables, but now I can only put it in the weapon/item slots.
currently, you have to have pets in the equipment slot if you want to have more than one! i believe this was a decision made so that people wouldn’t be inclined to have so much visual clutter around their characters, but that’s just speculation.