You can enable in-app messaging between Administrators, submitters, and/or reviewers (if applicable) for a submission or review phase in specific.
1. Go to Calls, and select the desired call
2. Click Template from the top bar
3. Next to the phase you want to update, click Edit
4. Under the Communication with Submitter or Communication with Reviewers, locate the Messaging and click the checkbox to Enable Messaging for this phase
5. Select which user roles are automatically added to a channel as members: Admin, Submitters Reviewers (On assignment)
6. Click Save in the right top corner
New message notifications will be displayed in the right top corner, next to the profile section. It will show the Call and submission name to which the message is related to, or you can click Show all Chats. For more information on how to manage All Chats, go here