Slot locking. I’ve always had a problem of dropping items when changing tabs as alt is my drop key (as i said last time) so i added slot locking. Pressing L whilst hovering over an item in your inventory locks the slot. When a slot is locked the item inside it can’t be picked up or dropped (this includes when inventory is closed). Trying to drop an item which is slot locked will result in a message which only you can see that tells you the slot is locked. The slot can be unlocked by pressing L while hovering over it again. When your inventory is open a translucent lock icon is over whichever items / slots are locked.

How it works:

When i go to drop and item, it checks whether the slot the item is in is locked. If it is then it cancels the drop. Same logic applies when trying to move it around in my inventory with mouse