A solução foi gentilmente postada no fórum do AutoHotKey por "VxE":
Capslock::
Gui, 93:+Owner ; prevent display of taskbar button
Gui, 93:Show, y-99999 NA, Enable nav-hotkeys: hjkl
Send {LCtrl Down}
KeyWait, Capslock ; wait until the Capslock button is released
Gui, 93:Cancel
Send, {LCtrl Up}
Return
#IfWinExist, Enable nav-hotkeys: hjkl
*h::Send {Blind}{LCtrl Up}{Left}{LCtrl Down}
*j::Send {Blind}{LCtrl Up}{Down}{LCtrl Down}
*k::Send {Blind}{LCtrl Up}{Up}{LCtrl Down}
*l::Send {Blind}{LCtrl Up}{Right}{LCtrl Down}
#IfWinExist, ; end context-sensitive block