You can only assign an issue to one user, but you can subscribe or mention other users in an issue so they have visibility. All users subscribed or mentioned in an issue will receive notifications about that issue, in addition to the person assigned to the issue.
Subscribe users to an issues:
Select an issue from the issues list (or click an issue pop up card) to open it in the left sidebar
Click the bell icon at the top of the issue panel (i.e. the user subscription button)
Search for a user to subscribe. Select their name. Once selected, they become subscribed to that issue (meaning they’ll receive issue notifications for that issue)
To unsubscribe yourself from an issue, click ‘Unsubscribe from Notifications’
Notify Multiple Users on an Issue
Mention Users in an Issue
You can mention someone using the @ symbol followed by their CoLab username in an issue description or in an issue comments. They will receive a notification about the issue, similar to if the issue was assigned to them.
Mention users in an issue:
To mention a user, type the @ symbol followed by their CoLab username either in the issue description field or in the issue comments box
Select their name from the list
Once their name is selected, they will receive an issue notification right away