https://maven.fabricmc.net/docs/yarn-1.20.5-rc2+build.1/net/minecraft/network/packet/c2s/play/PickFromInventoryC2SPacket.html

This can move items around in the Player's inventory by sending this packet. Sending a slot number within the player's inventory will move the item into the player's selected hotbar slot without firing obvious events on many servers. This can break a number of plugins, so having this would make debugging a lot easier.

Great idea! will add

It mutates the inventory. Most of the MC space isn't aware, but again, if you send for example Slot 10, it will move the item from Slot 10 into the selected hotbar slot. I don't believe there's a way to trigger it in vanilla without mods.

This packet is not listed as a SlotActionType, but if a general packet fabrication tool is added, this will go on the list.

can you record a video of what you mean?