Adding a vertex at the midpoint of a segment

Steps:

1. Click the Edit tool on the Editor toolbar and double-click the feature you want to edit.
2. Click the Sketch Properties button on the Editor toolbar.
When the Edit tool or a construction tool is active, you can press P as a shortcut to open the Edit Sketch Properties window.
3. In the Edit Sketch Properties window, select the vertex before or after the place you want to insert a new vertex. When you check a vertex in the Edit Sketch Properties window, the vertex is selected and drawn with a hollow, white box on the map. You can also select a vertex on the map to help you locate it in the Edit Sketch Properties window.
4. Right-click the selected vertex and click Insert Before to add a vertex before it, or click Insert After to add the vertex after it.
5. Click OK.