Items that are not placed or dropped while surfing the Inventory disappear when closing the Inventory using E or Esc

I expected to drop the custom Diamond Sword

Upon pressing E while having the Sword or any Item in hand it just dissappeared

1. Go into a World
2. Go into Creative Mode
3. Take any Item from the Creative Inventory
4. Drag the Item but do not put it down or drop it
5. Close the Inventory via E or Esc
6. Its gone, MAGIC

**This is an Issue because first Overall Map making and I think there was a bug like this in the past too... Please just fix it