1. You need the amulet, a heart container and any other item/block
2. Put the amulet in the first slot
3. open it
4. put heart container inside and close the interface
5. reopen it
6. hover over the other item in your inv and press 1 to swap it with the amulet (now you can move the amulet in your inventory)
7. Throw the amulet out and take the heart container back out
8. The amulet on the ground still has the heart containers inside

Please tell me what version of Minecraft, Baubley Heart Canisters, and Modpack you are playing so I can attempt to replicate.

I am playing the newest version of ATM8 and the mod version is 1.19.2-2.1.0

Thank you for your information.
This indeed is a dupe. and it works for ALL Canister using items, Vitality Blade, Soul Amulet and Heart Amulet.

But, other mods have a fix for this dupe as it is a Vanilla Exploit.
If the call action Denies the hotbar item switch, or Force Close the GUI before it can move.