Opening the Curios Inventory removes the Trash Slot.

I opened a issue at Curios github
TheIllusiveC4/Curios#47 (comment)
and they said they cannot fix it and the Slot have to be added to their inventory as well.

Try pressing T to toggle the Trash Slot. The slot works in nearly every inventory GUI.

Is it possible to enable it by default?

Currently only by shipping the TrashSlot.json in the modpack. #74