When performing a warm transfer inside the ECS Agent client that includes a 3-way conference where all parties are connected at the same time, the following steps should be followed:

  1. Click Consult  and contact the other Agent
  2. Click Start Conference to join all 3 parties together
  3. Click Stop Conference to put both calls on hold
  4. Expand the Telephony Sessions  to make both calls visible
  5. Click Retrieve  to take the caller off hold
  6. Click Transfer  on the Agent call to complete the transfer

Please review this video that illustrates this sequence of steps.