It seems that manual supports are not working in version 2.1. Ive used them many times in 2.0.1. I follow the normal process of clicking "Add new support structures", but they don't show up at all when I click. The little support beam doesn't show up when I move my mouse around either.
mine is woking on osx as well. let me ask, its the support size set real small? default is 4mm. if you lower it down to say 1mm then it takes alot longer for the support to be calculated. i accidently set it to .04 one time and it took over 5 min to calculate all the parameters. could your computer be sitting there processing?
i just double checked all this again to be sure and it does work just fine on my mac. same as it always has. i even threw a model on there and did 1mm support and it was calculated almost instantly. nothing weird with the mouse or pointer locations.