There is a bug on how Parallel 19 treats VM that uses all screens when maximized or full screen mode. When maximized, mouse over the top edge in external displays may not show the windows bar (it doesn't work for me 100% of time). The bar only shows up on my MBP's built-in display, and is not as responsive as Parallel 18.
If I successfully exited the full screen thru external display, then Parallel 19 thinks I'm still in full-screen mode, and will auto-hide Mac's application doc if VM is in focus.
If I successfully exited the full screen thru external display, then Parallel 19 thinks I'm still in full-screen mode, and will auto-hide Mac's application doc if VM is in focus.