When you're in the creative inventory, are looking in a random tab and want to go to the search tab, you usually press T to open the search tab. In this snapshot, the letter "T" is also put.
How to reproduce:
- Open a world in creative mode
- Open the inventory and go to a tab which is not the Search tab
- Press T
What should happen:
You should enter the search tab with an empty search box.
You enter the search tab, with the letter T already filled.