Hello Morgane Le Coadic,
Thank you for reaching out on the Microsoft Q&A forum.
You're right—the Power Apps interface has changed, and some steps in the MS Learn module might be outdated. Microsoft updates features frequently, so the content should be updated soon.
In the meantime, you can create a blank model-driven app by selecting Create → Start with data, choosing Existing tables, and selecting the Account table in Dataverse. From there, you can customize your app in the App Designer, then Save, Publish, and Share.
If you are still facing any issue, please let us know in the comments and where you are encountering this error along with the screenshot for reference. We are glad to help you.
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Thank you.