I
Set In
O
Set Out
X
Mark In and Out points for the clip under the playhead
Opt+I
Clear In
Opt+O
Clear Out
Opt+X
Clear In and Out
F9
Insert edit
F10
Overwrite edit
F11
Replace edit
Shift+F11
Fit to fill
F12
Superimpose
Cmd+U
Make subclip
Opt+U
Use custom layout 2
Cmd+Z
Undo