• Move by 5 keyframes : CRTL + Shift + ← or →

• Move a layer up or down : CRTL + ALT + ↑ or ↓

• Center the anchor point : CTRL + Double-click on the anchor point tool

• Adjust the size of your layer to that of the composition : CRTL + ALT + F

• Adding a marker to a layer : * or CTRL + 8 on MAC

• Change the type of your keyframes in one click : CRTL + ALT + CLIC

• Placing a position keyframe : Shift + Alt + p (t for opacity, r for rotation…)

• Adjust the length of the composition to the length of your work area : CTRL + Shift + X
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• Atint the beginning or end of the selected layer : I or O
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• Pre-compose selected layers : CTRL + Shift + C

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If the Mac version is not written down, it's because it's the same, and if the shortcut includes the CTRL key, it should be replaced by ⌘.