how can i drop items

keep pressing the shift key while clicking in it. This allow dropping even in close quarters.

Go to the inventory screen. Hold down the shift key while selecting the item you want to drop with the mouse. The object will be dropped when you leave the inventory screen and go back to the game.

Be sure to watch where it goes, dropped objects tend to bounce off into dark corners or drop behind you and roll under furniture. Some things, such as staffs like to fall through the floor and vanish. If you can, drop them onto a table.

To pick it up, without adding it to your inventory, mouse over it, A hand cursor should appear, do not click. Instead hold down the 'Z' key to grab it. You must keep the z key held down to continue holding it. This allows a crude placement of the object. To place an object precisely and lock it in place, you will need a mod called Decorator Assistant.