What happens if I select the "Overwrite thread(s)" option during restore?

If the admin chooses to overwrite the Slack threads while restoring an entire conversation or a specific thread to a particular point in time, the existing version will be deleted, and the conversation will be restored with the version available in the backup snapshot. By choosing to overwrite the conversation, not only do the deleted conversations get restored but also the ones that have been modified will roll back to the point in time given in the backup snapshot. 

If the admin does not choose to overwrite the Slack threads, only the deleted threads will be restored to the associated channels. The threads which are already present in the Slack application will be skipped during the restore even if a modified version exists in the selected snapshot.