The Symmetric Edit tool maintains the symmetry of a path segment while you drag. No matter where you click on the segment or where you drag, the curve remains symmetrical between the anchor points.
TIP: For precise control and moderate reshaping of a curve, click near the middle of the path segment and drag. For more dramatic changes, click near an anchor point and drag.
After reshaping a path segment with the Symmetric Edit tool, you can Shift-click on the segment to convert the nearest anchor point to a smooth point. Doing so will adjust the edited path segment to correspond to the flow of the adjacent path segment.
In the Xtream Path 2 panel, you control the behavior of the tool with a pair of options:
Fixed Length Rate
When selected, this option determines how much change will be applied to a segment with a drag of a specific distance. It is the ratio of the direction line length to the path segment length. The greater the percent, the more a segment is altered as you drag. For substantial changes to large objects, a higher value reduces the distance you'll need to drag.Fixed Open Angle
This value determines the shape of the curve when you first click on or drag a path segment. The angle refers to the anchor points' direction lines in relation to the path segment after the alteration. The angle can range from 0 degrees (which can convert a circle to a square) to 180 degrees. Entering a specific value and clicking on a path segment gives you precise results. You can also continue to drag a path segment after the initial angle is applied.TIP: Hold down the Shift and Option keys (Mac) or the Shift and Alt keys (Windows) and click near an existing anchor point to load its values into the Fixed Length Rate and Fixed Open Angle fields.
Using the Fixed Length Rate in conjunction with the Fixed Open Angle option enables you to quickly create precise curves. For example, alternating concave and convex curves can convert a polygon to a gear shape. Click and drag a short distance inward/outward to create concave/convex curves.
The Xtream Path 2 panel also offers the option of showing or hiding the direction lines for the path's anchor points. You can hide all direction lines, show only those for the path segment being edited, or show direction lines for all of the path's anchor points. You can also elect to show the path segments direction lines while dragging a path segment. When visible, direction lines can be dragged with the Symmetric Edit tool.
When positioned over an anchor point or direction line rather than a path segment, the Symmetric Edit tool functions as Illustrator's Direct Selection tool. You can drag anchor points or direction lines to adjust the shape or an object.
In addition, holding down the Option key (Mac) or the Alt key (Windows) converts the Symmetric Edit tool to the Add Anchor Point tool (when over a path segment) or the Delete Anchor Point tool (when over an existing anchor point).
Example: