Co-Authoring is available in Microsoft Teams on documents stored to enable multiple people to work on the same document simultaneously. Documents stored in your teams are accessible to every team member, and they can collaboratively co-author documents.
How to Co-Author a Document in Microsoft Teams?
To Co-Author a document, you can open it and click on the Edit button and then choose any of these three options: Edit in Teams, Open in Desktop App or Open in Browser.
There is no need to check out files or worry about if one of your colleagues has the document open. Just open the file you need to edit, and if other Team members are editing it too, your changes will be seamlessly merged as you work. Microsoft Teams indicates if any other user opened the document and made changes.
Invite Users to Co-Author
To share a document with additional users, you’ll have to open the file in Office Web Apps or in the Office desktop client. The Teams editor doesn’t have that feature yet. Click the arrow next to the Edit button and choose “Open in Desktop App” or “Open in Browser”. The edit button with the choices expanded and an arrow pointing at the drop-down button.