To get a ConnectorProperty to show with a dashed line to its Connector in an IBD (or in the structure compartment of a Block symbol) drag an AssociationBlock onto a Connector to set it as its Type in an IBD. A ConnectorProperty will be created and a ConnectorProperty symbol shows on the IBD with a dashed line to the Connector.
Once the dashed line appears don't remove it or the ConnectorProperty symbol
For full instruction visit this detailed example:
Or visit this external MD SysML help page.