In the Drawing view, you can set up your onion skin to display marked drawings only, in the same way that you flip through your drawings marked as key, breakdown or in-between drawings—see About Marked Drawings
From the top menu, select Windows > Toolbars > Onion Skin.
In the Tools toolbar, click the Show Onion Skin button.
In the Timeline view, pull on the blue arrows to extend the number of drawings displayed in the onion skin preview.
In the Camera View or Drawing View toolbar, use the Onion Skin Add One Previous Drawing , Onion Skin Reduce One Previous Drawing , Onion Skin Reduce One Next Drawing and Onion Skin Add One Next Drawing buttons to adjust the span of the onion skin frame by frame.
In the Onion Skin toolbar, enable the markers you want to see in your Onion Skin preview.