ctrl-z: undo last editor command. Undo stack is 10 levels deep.
ctrl-x: cut the currently selected piece or pieces
ctrl-c: copy the currently selected piece or pieces.
ctrl-v: paste the current clipboard contents at the cursor.
R: rotate the current piece.
P: will pick the current piece up into the entity editor. This is handy for quickly grabbing a piece without putting it
into adjust mode (which also will change to that pieces layer). This can be a faster way to grab a texture into another layer.
Delete key will delete the current piece if in adjust mode.
The arrows keys can be used to nudge the currently selected piece or pieces. If working on a layer in grid mode then an arrow
key press will move object one grid section at a time otherwise the object will move one pixel per arrow key press.
Right mouse button will pick the current piece up into the entity editor, switching to that pieces layer and placing that piece
into adjust mode.