Here's a reference of the hotkeys you can use with the MiSTer. Hotkeys are useful at saving time and there are some hotkeys which do things you can only do with a keyboard or gamepad. Some of these hotkeys only work in the Main Menu core, others will work inside emulators as part of the gameplay, and some will work in all instances.
In any core, with OSD closed
Hotkey
Description
F12
Open the Menu/On-Screen Display
Alt+F12
Open core select menu
Win+Print Screen
Take a screenshot (upscaled)
Shift+Win+Print Screen
Take a screenshot (raw output)
Left Ctrl+Left Alt+Right Alt
Press "User" button, usually resets current core, same function as IO board button
Left Shift+Left Ctrl+Left Alt+Right Alt
Full Reboot/Reset, same as IO add-on board Reset button
Controller: Button + Menu hotkey
Turn on/off turbo/autofire for the pressed button
Controller: Direction + Menu hotkey
Set rate of turbo/autofire in milliseconds (ms)
With the OSD open, in any core
Hotkey
Description
F12
Close OSD
F11
Pair Bluetooth controller
Hold IO Board OSD Button
Alternate method to Pair Bluetooth controller
Left
Go to information screen (shows currently selected INI file and volume)
Right
System screen (change core, set filters, gamma, etc...)
Controller: Back + R/L/U/D
Select Alternate INI file if defined (Default/Alt1/Alt2/Alt3)
Controller: Select
Expands submenus in the OSD when highlighted
Controller: Shoulder Buttons
Cycles through the OSD options in a core in either direction
In the Main Menu core only
Hotkey
Description
F1
Switch background type (static, wallpaper, color bars, black)
F2
Hide / Show core dates
F9
Open Linux terminal / command line interface, use F12 to go back to menu
Controller: LB + X / Y
Test the rumble motors on your controller
Core-specific hotkeys
Some computer cores
Some computer cores make use of the Windows key (Win) on your keyboard.
Hotkey
Description
Win+F12
Open the OSD
Cores that support savestates
Very few cores support savestates (NES, PSX, GameBoy, GBA, WonderSwan, AtariLynx). There are 4 savestate slots available. In those cores there is a standard savestate button you can assign on your controller (we'll call that SaveStateBtn here):