The only way for Slack and Microsoft Teams users to collaborate on a file together is if the user posts a Sharepoint/OneDrive link. Anyone in the chat can click the link and work on the file, and Sharepoint/OneDrive will handle the permissions/versioning.

On the other hand, if the user uploads a file into the chat (via the paperclip icon, for example) then MIo will take a copy of that file and post the copy (ie, a duplicate) into the other messaging app. Then, the file will be stored twice: once in Microsoft Teams, and once in Slack.

Did this answer your question?