Apple's latest and greatest, the El Capitan operating system, generally works just fine with Mellel... But there is a small 'but': It seems that in full screen mode, when splitting the screen (ad El Capitan will permit you to do) Mellel, well, er, displays the document without regards to this special mode.
This probably got our El Capitan users slightly miffed. We were too, but the cavalry is coming, by way of Mellel 3.4.4 which will be released soon and fix this problem.
Ori from RedleX