Hi Mouettes,
Thanks for reaching out to our Microsoft Community Forum and please accept our sincerest hope that all is well.
We understand you'd like to the ability to hide or archive folders in Outlook for mobile (iOS and Android) to make navigating through multiples folders easier.
So the mobile versions of Microsoft 365 apps like Outlook have a limited feature set compared to their full desktop counterparts and some of those limitations includes the very same features you've mentioned above. To put it simply, the mobile versions of Microsoft 365 apps are designed to imitate just the basic functionality of the desktop version of the apps and not all the functionality.
This might not be what you had expected of the mobile apps so at this point we highly recommend that you use the built-in feedback feature of the apps to make you voice heard. As noted in our How do I give feedback on Microsoft Office? guide: "We'd love to hear from you. Let us know what's working well, if there are problems with our products, or if you have ideas about new functionality that would improve your experience. Your feedback goes directly to our products teams and helps us shape the future of Office for users around the world."
Feel free to reply to this thread if you need further clarification.
Respectfully,
Glenn Rue
Consumer M365 Forum Moderator
Microsoft Community