In Manage participant task, adding participant need default role out of two values

Summary:

In Performance Management, we need two types of participants, One is 'Matrix manager' who has full access to view worker, manager and participant ratings, comments and questionnaires. And another participant role: 'Stakeholder' who should not have that access. So defined that using performance role task.

Then in General tab of performance template, added these two roles (Stakeholder, Matrix Manager). Matrix manager request feedback going automatically as it is selected, as defined in process tab of performance template. Please refer below screenshot..

Now my requirement is when line manger adding participant, we need default role as Stakeholder and this role field should be