Dear Gabriele Barone,
Good day! Thank you for posting in Microsoft Community.
According to your description, it looks like the Document Folder pointed out with the green arrow is a document library. You want to move Task List to the document library in SharePoint.
We're afraid it's not available to do so.
Generally, document library can store files such as Word document, Excel workbook, PowerPoint presentation, OneNote notebook and PDF files. While Task list is usually stored in Site Contents page in a SharePoint site.
We apologize it cannot meet your requirement.
We understand it's a good addition to the current features of SharePoint, thank you for pointing this out. Microsoft continuously aim to improve the features of O365 Product.
Your voice is important to us. We sincerely recommend and encourage you send feedback to SharePoint feedback community, it's the specific platform to let the developers know your requirements and comments, Other members who has the same requirement as you will vote your idea in the future. This is the best way to help us improve the product and make it better for you and others.
Thanks for your understanding! Hope you have a nice day and stay safe.
Sincerely,
Tina | Microsoft Community Moderator
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