The Object Properties... dialog and all of the commands in the Arc submenu affect existing arcs, specifically those currently highlighted. To affect future arcs as they are created, use the "New Arcs" preferences (in menu File / Preferences..., "General" section, "New Arcs" tab).

The dialog that appears allows you to set defaults for specific types of arcs. The rigid, fixed-angle, and slidable constraints may be controlled with this dialog, as can the directional, and end-extension properties. |

It is also possible to specify the default width and angle for newly created arcs. The angle field is the preferred angle increment in degrees for newly created arcs (90 for Manhattan, 45 for Manhattan plus 45-degree angles, and 0 for any angle). The "Pin" is the default node to use when joining two of these arcs.

The checkbox at the bottom lets you determine whether or not sounds are played when arcs are created.