Feature is in vanilla as of 1.16 and should be deprecated.
also the quark version ignores slotClick.

yes, it's available in vanilla, but not in the inventory.

yes, it's available in vanilla, but not in the inventory.

As of 1.16 it is in inventory as well.

yes, it's available in vanilla, but not in the inventory.

As of 1.16 it is in inventory as well.

I Dont Think So

yes, it's available in vanilla, but not in the inventory.

As of 1.16 it is in inventory as well.

I Dont Think So

I do think so. In fact I have tested (~20 seconds ago). Vanilla 1.16.3 does in fact have off hand inventory exchange.
If you press f when hovering over a slot it will put/pull an item in the slot to/from the off hand. :) "Thinking so" is a handy tool to have, but verification is much more viable in GitHub posts 😄

Flanks would know as I used his mod + the reported bug here to dupe items 🙃