Hi @Clémentine Lorotte de Banes ,
Welcome to our forum!
According to my test, when using Outlook for Windows or Outlook Web App (OWA) to access your calendar, you can set the status of your calendar items to one of five options:
When using Outlook for Mac or any other client, you will see only four:
Besides, based on my search, the status Working Elsewhere is only supported and recognized by Outlook for Windows and OWA. If you sync your calendar with another client/app, including any mobile apps, all items marked with that status will show as Free. This means that anyone looking at your calendar's availability from another client will not know that you are unavailable if your items are marked with Working Elsewhere.
To work around it, it is recommended use another status.
Hope this can help you!
If the answer is helpful, please click "Accept Answer" and kindly upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.