In Site Library vs. In Channels

Public Channels folders are all contained in site library sections, whereas Private Channels folders are not. Additionally, it includes all folders and files produced by the SharePoint site; for instance, folders and files produced using the ribbon's "+New" function appear in the "In site library" area.

Therefore, the In channels section is accessible to all Team members, but the Private Channel folder is only visible to members of the private channel.

This modification to the SharePoint document library is used to distinguish between folders created by the SharePoint site itself and folders related to Teams channels.

Second, you said that you received an error notice when you attempted to resync the document libraries from One Drive. To help us identify the behavior and do additional research, we would need to check the following with you:

Did you click the notification to see whether the file was already in the OneDrive folder?