Outbound calling is not currently built-in to Flex. However, we do offer the Twilio Flex Dialpad as a limited support pilot feature. Using Dialpad, agents can place outbound calls, conference in other agents, and use DTMF touch-tone keypresses for navigating phone tree menus.
Dialpad can be added to your Flex instance from the Flex Admin's pre-release features page. For full details setting up and using Dialpad, see Dialpad - End User Guide (Twilio Docs).