But what about when 2 people are editing a Word document from SharePoint Online while using the full Word desktop application?
If two people open the same Word document in the desktop app, you will see a visual indicator in the bottom-left corner of Word informing you there are 2 people editing the document.
What if there is a "save conflict"?
Note: This only works while 2 people are editing the document directly from SharePoint Online. If you are using OneDrive For Business, and you opened the file from the local cached files list, you will not see this functionality.