In the Timeline view, select the cell on which you want to draw.
In the Tools toolbar, select the Polyline tool or press Alt + _.
In the Camera or Drawing view, click and drag to create a point and a Bezier handle to shape your line.
Click a new area and drag to create a second point and Bezier handle.
Press Alt to pull only one handle, instead of two.
Press Shift to snap the handles to 45, 90, or 180 degrees.
Repeat the previous step until your shape is completed.
Press Ctrl (Windows/Linux) or ⌘ (macOS) and click to release the Polyline tool from the current path or shape that it is creating. Continue to use the tool to make multiple, independent paths or shapes.