Tried latest hourly build (9/28), no luck.
Previously, in 1.8.3 and prior, and with all versions of OSX including High Sierra, one was able to rotate through all open windows using Command + ~ (including using the shift key to rotate in the 'opposite' order). As of 1.8.4 it only rotates through last two opened windows.
This is fine when one open window is the Monitor, thus ensuring the monitor window and its associated sketch are only rotated through, avoiding possible erroneous changes to other sketches. However, when monitor is not open, it only rotates through last two opened files. Is this a bug or an "improvement?" I suggest keeping the new functionality/logic when monitor open, but going back to previous functionality when monitor not open.