If you’d rather change the default setting for yourself so that a single left-click opens in the desktop app always, there are two places you can change your file opening preference – a file’s open menu or your Teams settings.
Note: Desktop/app will only be available as an option if you have Office version 16 or newer.
Always open Teams files in the desktop app | Method #1 (from a file)
To change your default file opening preference from an individual file’s menu, right-click the file, select Open, then select Change default.
Then choose Desktop app and Save. Now Teams will always open Word, PowerPoint, and Excel files in the appropriate desktop application.
Always open Teams files in the desktop app | Method #2 (in your Settings)
Alternatively, you don’t need to find a file first. Simply use the ellipsis (three dots) in the upper right corner of Teams and choose Settings.
Then select Files from the left and choose Desktop app from the dropdown menu. You change is saved automatically.
Always open Teams files in the Desktop app | Bonus method (prompt after opening one-time in desktop)
There is one more way to change this setting, but it’s less straightforward so I’m deeming it a “bonus method.”
If you do choose to right-click > Open > Open in app one time for a file, when you return to Teams it will prompt you to let it know if you were just opening in the desktop app this one time, or if you would like to go ahead and change your setting to always open Teams files in the desktop app.
Ref: https://support.microsoft.com/en-us/office/edit-an-office-file-in-teams-257a5e88-205a-4fb5-bbf1-c78c3e64de86?s=09#desktoporwebapp