Keyboard Shortcuts in the Editor

Undo Last Change:  Win/Chromebook: Ctrl-Z  | Mac: Cmd+Z
Redo Previous Change: Win/Chromebook: Ctrl-Y | Mac: Cmd + Y
Redo Last Undo: Win/Chromebook: Ctrl+Shift+Z | Mac: Ctrl+Cmd+Z

Arrow Keys: Nudge frame
Shift+Arrow Keys: Nudge frame in smaller increments

Copy: Win/Chromebook: Ctrl-C  | Mac: Cmd+C
Paste: Win/Chromebook: Ctrl-V  | Mac: Cmd+V

Select All: Win/Chromebook: Ctrl-A  | Mac: Cmd+A

Zoom In: Win/Chromebook: Ctrl++ | Mac: Cmd++ (Plus key)
Zoom Out: Win/Chromebook: Ctr+-  | Mac: Cmd+- (Minus key)
Dialing the mouse wheel up/down while no element on the canvas is selected also changes the page zoom level.

Change crop on image frame: Hold Ctrl (Win/Chromebook) or Cmd (Mac) while dragging on the frame (Unlocks the frames width-to-height ratio)

Zoom image within its frame: Hold Ctrl (Win/Chromebook) or Cmd (Mac) while dialing your mouse wheel up.down.

Drop an image onto the canvas so it appears behind other frames: Hold Ctrl (Win/Chromebook) or Cmd (Mac) dragging the image from the right-side preview to the canvas. When you drop the image, it will be behind the other images.

Select an image behind a portrait grid: Hold Ctrl (Win/Chromebook) or Cmd (Mac) to select the image. It will be selectable behind the grid.