These are the keyboard shortcuts for Elgato Game Capture HD. 

The "Command" key is also known as the "Apple" key, and has a symbol similar to a cloverleaf (⌘).
 

Command	Mac	Windows
Global
Switch to Capture	⌘ + Shift + 1	Ctrl + 1
Switch to Edit	⌘ + Shift + 2	Ctrl + 2
Toggle Fullscreen	⌘ + Control + F	F11
Leave Fullscreen	Esc	Esc
Show/Hide sidebar in fullscreen mode	F10	F10
Capture/Editor
Start/Stop Recording	⌘ + R	Ctrl + R
Enable/Disable Live Commentary	⌘ + L	Ctrl + L
Start/Stop Live Streaming	⌘ + Option + S	Ctrl + Alt + S
Mute/Unmute	⌘ + Option + ↓	Ctrl + M
Enable/Disable Preview	No Shortcut	Ctrl + P
Play/Pause	Space	Space
Fast Forward	Option + →	Alt + →
Fast Rewind	Option + ←	Alt + ←
Screenshot to Clipboard	⌘ + Option + C	Ctrl + Shift + C
Screenshot to Desktop	⌘ +  Shift + C	Ctrl + Alt + Shift + C
Timeline
Select All Clips	⌘ + A	Ctrl + A
Remove Clip Selection	⌘ + Shift + A	Ctrl + Shift + A
Select Clip At Playhead	⌘ + Option + A	Ctrl + Alt + A
Select Previous Clip	⌘ + ←	Ctrl + ←
Select Next Clip	⌘ + →	Ctrl + →
Zoom In	⌘ and +	Ctrl and +
Zoom Out	⌘ and -	Ctrl and -
Jump to First/Start Position	Home, Return	Home
Jump to Last/Stop Position	End	End
1 step* backward (1/4 sec)	←	←
40 steps* backward (10 sec)	⌘ + Option + ←	Ctrl + Alt + ←
240 steps* backward (60 sec)	Shift + ⌘ + Option + ←	Ctrl + Alt + Shift + ←
1 step* forward (1/4 sec)	→	→
40 steps* forward (10 sec)	⌘ + Option + →	Ctrl + Alt + →
240 steps* forward (60 sec)	Shift + ⌘ + Option + →	Ctrl + Alt + Shift + →
Split/Cut clip into two parts	⌘ + Shift + S	Ctrl + Shift +S
Undo	⌘ + Z	Ctrl + Z
Redo	⌘ + Shift + Z	Ctrl + Y
Restore original segmentation for current video		Ctrl + Alt + Shift +Z
Delete currently selected clip(s)/segment(s)	Delete, Backspace	Delete
Delete clip	Delete, Backspace	Delete
Show advanced settings when opening device settings		Ctrl + Mouse Click
Stream Command/Overlays
Select Scene	0-9, ⌘0 - ⌘9	0-9
Remove all overlays from scene	Option + Mouse Click	Ctrl + Shift + Delete
Move selected overlays one pixel up / down / right / left	n/a	↑, ↓, →, ←
Move selected overlays ten pixels up / down / right / left	n/a	Shift + ↑, ↓, →, ←
Bring selected overlays one step to the front / back	No Shortcut	Ctrl + ↑, ↓
Increase size of selected overlays (by one pixel along the short edge)	n/a	"+" , "-"
Increase size of selected overlays (by ten pixels along the short edge)	n/a	Shift + "+" , "-"

Please Note: * 1 step means 1 GOP on Windows, which is about 0.25s for GC recordings