can't trash items in other blocks in creative tabs

I just played minecraft 1.12 on creative mode, because i'm making a map for polish youtuber. I was happy to get acces to all of items, but i suddenly picked something. It wasn't very convinient. I tried to take it to creative tab and drop it to some other item, but i just cames back with some cool animation. I could deleting like thet before 1.12, but I needed to drop it in empty space. I will show it on video i attached... nevermind... I'll show you in graphic.

() - This is item i want to thrash

• - Other block in creative tabs
  I'm putting () into *
  () goes back whre i started to drag.
  Understood me? Good.