Choose the library tab
D&D a button to the content panel.
Select the id tab
Now click your button again in the content panel so that the content panel gains panel focus
Now click a few pixels underneath the "inject in controller" property in the identity tab - the identity tab should get panel focus but it does not.

It seems that the area between the lowest property and the horizontal splitter does not receive the mouse event. This is also the case if the last section of the tab is closed and you click below it.