I find this to be a very cumbersome way to navigate on mobile.
If you don’t already know to look in the sidebar, there’s no obvious way to know the sidebar is filled with context specific options.
To navigate between pages, you have to reach the top corner of the screen, scroll to the bottom of the sidebar and do a percise touch to the correct submenu you want. Visually, the admin menu is indistinct from the rest of the sidebar.
In contrast, with the old method, you are immediately presented with the top level sections that are 0 to 1 swipes away and enable you to drill down to find the exact admin subsection you want instead of requiring the user to know in advance.
Overall I like the idea but I think it makes mobile UX worse, not better. I find in general I almost never use the sidebar on mobile. I think it is just too cumbersome to open and maybe the options are too detailed/tiny.
I compared other apps and one thing I noticed is that access to the sidebar is typically a very simple gesture. Discord and Twitter let you just do a quick horizontal swipe to open the sidebar. The ebay app has a button on the bottom menu. My banking app opens the sidebar when you press the back button. The common theme is that all these gestures I would normally do without even thinking but opening the Discourse sidebar on mobile feels like a very deliberate action.
I think for this experimental sidebar to work effectively for me, you need easier access to the mobile menu and also to hide all the non-admin specific settings. The “back to the forum” button is actually a nice touch because it really makes it feel like you are in a separate context when navigating the admin section.
But yeah I guess my advice overall for Discourse is that if the sidebar is going to become an essential navigation feature on mobile, you really need to improve how easy it is to open and close. The fact that my phone is a larger model and that the top part of my screen is currently dead zone for touch input has especially highlighted how inaccessible the sidebar is for me.