Right angle connectors and straight connectors are actually two different kinds of objects, like circles and squares are different kinds of objects.
Unlike circles and squares, however, you can change the connectors from one type to another.
For connectors drawn with the connector drawing tools or in a Flow Chart: Select the connector you wish to change (see below) and go under the Layout menu to Connectors... Just click the kind of connector you wish to change to and hit the OK button.
For connectors in an org chart, select the connectors you wish to change and go under the OrgChart menu and select Connector Settings... Make the changes you would like and hit OK.
To select the connectors, simply click on the connector line itself. To select multiple connectors, hold down the shift key and click on the connectors you wish to change. To select all connectors, go under the Edit menu and choose Select All, or hit Command-A.