Really late answer here. I don't know any native way of doing this, but I wrote this Autohotkey script that hides the taskbar if the desktop has the focus. I couldn't get it to auto-show the taskbar on mouse hover if the desktop has the focus, but if any other window is activated first the mouse hover works. This script also completely hides the taskbar (at least on latest Win 10). So no ugly grey lines at the bottom. I also added the following hotkeys:
Show taskbar: Left Ctrl + Right Alt + s
Hide taskbar: Left Ctrl + Right Alt + h
Kill script: Left Ctrl + Right Alt + Escape
The "Kill script" hotkey will work everywhere and the two others works if the desktop has focus. If your keyboard has the Altgr key, this can be used instead of Left Ctrl + Right Alt. If you spend a few minutes with Autohotkey, you can change them to whatever you want. Autohotkey (current stable release) is needed to run it (free and open source).
#NoEnv
#SingleInstance,Force
#Persistent
SetWinDelay,0
GroupAdd, DesktopGroup, ahk_class Progman ; Adding both classes of desktop to the group "DesktopGroup"
GroupAdd, DesktopGroup, ahk_class WorkerW ;
Loop {
IfWinActive, ahk_group DesktopGroup
IfWinExist, ahk_class Shell_TrayWnd
{
WinHide,ahk_class Shell_TrayWnd
WinHide,Start ahk_class Button
}
Else
WinWaitNotActive, ahk_group DesktopGroup
Else
IfWinNotExist, ahk_class Shell_TrayWnd
WinShow,ahk_class Shell_TrayWnd
WinShow,Start ahk_class Button
}
<^>!Esc::ExitApp
#IfWinActive, ahk_group DesktopGroup
<^>!s::
{
WinShow,ahk_class Shell_TrayWnd
WinShow,Start ahk_class Button
Return
}
<^>!h::
{
WinHide,ahk_class Shell_TrayWnd
WinHide,Start ahk_class Button
Return
}
#IfWinActive
License: WTFPL