In 1.12 and lower I'm able to bind controls to the capslock key. However, with 1.13 I'm no longer able to do that.
On Mac the capslock key when enabled continuously fires as if you're holding down another key, this makes it extremely useful for continuously placing blocks or other things that are repetitive. Since the first beta release of 1.13 I've not been able to bind controls to it.
In addition to the capslock key not registering, I have a Logitech Performance Mouse MX, http://support.logitech.com/en_us/product/performance-mouse-mx that has four additional buttons, in 1.12 and lower these registered as middle click buttons (which I have assigned to block picking). In 1.13+ the game doesn't detect them.
Again 1.12 and lower, the capslock key and the additional buttons on my mouse registered just fine. In 1.13, they do nothing.
MC-121376 Cannot bind "caps" key in control settings