MC version: 1.21.1
inmis version: 2.8.1
fabric version: 0.16.5

Ender pouches can be equipped into the backpack trinket slot.

If an Ender Pouch is equipped and the hotkey to open the equipped backpack is pressed then the most recently opened backpack that is still in the player inventory will open instead of the Ender Pouch.

If no other backpack is in the player inventory then pressing the hotkey for the backpack will do nothing.