Storing documents locally or in cloud services from within Teams
Sorry to know that:)
If you are the owner of the Teams group and have access to the settings, then you should be able to configure the settings so that the file opens in editable mode. You can do this by navigating to the Advanced Settings section in the file's SharePoint library, and then check the box for 'Open in edit mode'. Once you have done this, the file should open in editable mode when you access it using the Word app on the desktop. Additionally, you can also assign specific permissions to different users, or groups of users, to determine who can open the file in editable mode.