I'm running the latest version os El Capitan along with the latest version of Win 10. I think I have a "Boot Camp" installation if it makes any difference. My MBA boots to OS X and I then access Win 10 via Parallels. Everything seems fine. However, when I'm in Windows and want to check something on the OS X side, I usually have to shut down Parallels to get to OS X. OCCASIONALLY, when I move the mouse pointer somewhere along the bottom of the Windows home page, the OS X dock appears, which allows me to switch to OS X WITHOUT shutting down Win 10. I'm not sure if it's some keystone or mouse click or just some movement of the mouse pointer that pops up the OS X dock as it happens so fast, I don't know what I did to make this happen. Can someone tell me how to do this fast switch without shutting down Windows? Thanks
Are you in full screen mode? If so, you can turn off full screen mode and have windows run as a window. The other thing you can do to quickly switch is just swipe 2 fingers on the magic mouse or three fingers on the trackpad to quickly switch between windows and mac.