I don’t know why:sob:，And I tried solve it but I failed. 
hi, there!
move your mouse over to the line between colour swatches and timeline. the cursor should change to arrow with heads on both sides, click and drag to right to reveal the canvas.
if this only expands the palette area, move the mouse slightly more to the right and click and drag again.
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Oh, dude! You save me!!!
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