I'm not sure about the right place to post this. I found this place after I posted at the Pump in English WP, here.
I felt mobile view was ignored in favour of the app which I definitely think has a way lower userbase. I have this basic UI feature in mind, which is just what the app has. The persistent scrollbar for the Table of Contents. The summarise what I raised there: "the lack of an easy way to scroll through the Table of Contents for any decently sized article. Try it on mobile view, it's horrible. The app, however, has that nice scroll bar: which is persistently present as you read and can collapse, showing the relevant (sub)sections for even quickly jumping to. You won't get lost in an article wondering how to get back to a said section that was on your mind."
Besides this, I'm kind of lost here. One: how do I test Advanced mobile contributions, the main page says it's not deployed yet but it's in Beta? Two: Have I put my above UI suggestion in the "right" place?