If a particular approver is not visible in the approver dropdown list, the user can follow the below steps to add a new approver.

1. The user can add approver by navigating to the Admin module and then the Workflow tile.

2. Click on the Test Request workflow process tab, under the Action column click on the add approver button to add the users to the approver's list.  The user can add the Test plan approvers and Report approvers.

3. The user needs to have atleast 'Read' permission to access the Admin module and 'Read' permission to access the workflow tab. Finally, the user needs have 'Create' permission to  update any workflow process.