Connection Definition PropertyManager - Dimensions Tab

You can select the dimensions of the connection element and then modify them when you insert the connection element.

Click Define Connection Element (Structure System toolbar) or Insert > Structure System > Define Connection, and select the Dimensions tab.

Dimension Group

You can create different dimension groups and select dimensions in the graphics area.

New Dimension Group Creates a new dimension group.
When you insert the connection element, you can edit the selected dimensions.