What I expected to happen was...:
Use of the mouses' middle button should function to select blocks player is pointing at in creative mode
What actually happened was...:
Function fails to select block; even if re-toggled or set to another key-binding. Player must enter creative menu to manually pick blocks.
Steps to Reproduce:
1. Create world in version 1.14
2. Enter Creative Mode
3. Attempt to select block using "Pick Block" Default is Middle Button.
Can't reproduce, works for me