There are 2 things that could be added to the game to make npcing items and transferring items to your retainers easier.

The first would be adding a way to "mark" items as a normal inventory item and having a way to disable viewing of the items marked while selling items to an npc or transferring items to retainers keeping a simple way to toggle viewing them in the inventory screen.

The second would be a simple "new items" view. It would display any items added to your inventory within the last 48 hours and again being a simple way to toggle the viewing between the filtered and non filtered items.

Thanks.