This is currently not possible. The functionality of adding a participant is only available after an issue's creation. However, there is a feature request on that, as you can see HERE.
And you can see a workaround on this conversation https://answers.atlassian.com/questions/39134037
We're looking for participants for a workshop at Atlassian! We need Jira admins who have interesting custom workflows, issue views, or boards. Think you have a story to sha...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs