I generally have my mac laptop configured to use 2finger-tap & control-click for second-button/right-click purposes.

Neither of these were working. I can no longer remember whether they worked briefly before they stopped, my apologies.

I tried to specifically set control-click to work, but the controls currently do not accept modifier keys EXCEPT as single keys. I set it up as a single key which solved the problem for using objects, etc, but did NOT allow me to manipulate piles of objects (especially dropping one, which I need frequently). The game is effectively unplayable unless I can split piles and drop singles effectively.

I went to and from the key control settings, trying to find a way that might work, but at some point clicking FAILED COMPLETELY. There was no way to gracefully exit minecraft, and force-quitting it cemented the problem in my OS. It took me about an hour to negotiate quitting various applications as gracefully as possible and still had to force shut down my mac. It restarted with the problem still in place, but this time I was able to successfully do a normal shutdown and it finally rebooted clickable again.

I am sorry this report isn't more specific. The ramifications were sufficiently serious and stressful that I do not want to explore recreating this.