Items finicky when changing slots

I find it difficult to change items into different item slots. For example moving Trinity Force from item slot 1 to item slot 3. I'm not sure what the criteria has not be made, ie the cursor had to be in the box, or the box corners need to line up, but it seems more often than not the item will not change over unless I have it in the exact right spot to the nano meter. PLEASE MAKE IT EASIER TO MOVE ITEMS QUICKLY! Oh and please don't tell me about presetting the item slots when creating and item set, I already know about that. Sometimes you still need to move an item.