The following keyboard shortcuts work in the Crater Editor:
Delete, Backspace - Deletes the selected element
Shift - Hold down the shift key to select multiple elements
←, ↑, →, ↓ - Moves the selected element
Ctrl + A, Ctrl + 1 (Numpad) - Selects all the elements
Ctrl + X - Cut
Ctrl + C - Copy
Ctrl + V - Paste
Ctrl + Z - Undo
Ctrl + Y - Redo
Ctrl + (Numpad) - Zoom in
Ctrl - (Numpad) - Zoom out
Ctrl + 0 - Zooms out to the smallest zoom value
Ctrl + S - Save changes
Tools:
Esc - Unselects element from the library when placing it
Learn more about keyboard shortcuts for the Crater Editor (for Mac).