Hi @sanae
If you try to access the dash.page_registry from within the pages folder, then it’s likely that the page_registry dict is not complete. The dict is created when dash.register_page() is called when loading each page from the pages folder.
To get around this issue, you can create the offcanvas menu from the app.py file or by creating in it a function. You can see an example of this in the dash-labs docs: /docs/demos/multi_page_layout_functions