In the Score Editor, select the arrow tool in the toolbar (the first one on the left). Make sure the symbol object is selected in the object palette. Select a crescendo by double-clicking on the start of the crescendo. The Edit menu will appear. Choose the symbol editing operation you would like.
If you select Edit from the Edit menu, three little diamonds will appear at the left, right and center of the crescendo. You use these control points to shape and move the crescendo. Click on a control point to select it and drag it around to shape or move the crescendo. Alternatively you can move a control point around using the arrow keys. You can move between control points by using the TAB and the SHIFT+TAB keys as well as by clicking on them with the mouse. The middle control point is used for move the crescendo and the outer control points for setting the start and end points of the crescendo. When you are finished shaping and positioning your crescendo, click the right mouse button or press the ENTER key to enter it into the score. If you don't want to accept the edits you've made, press the ESCAPE key.
While editing a crescendo, press L to level the crescendo, F to flip it, and PAGE UP and PAGE DOWN to change the angle of the crescendo.
You can also erase or move symbols such as a crescendo using the other tools in the toolbar. Make sure the symbol object is selected in the object palette. Select the tool you want and apply the edit by clicking on the beginning of the crescendo (to erase using the eraser tool) or by dragging the crescendo up, down, left or right.