I've tested this with no add-ons or scripts.
On kiwi browser on Samsung s23 latest software etc etc. I toggled desktop view by clicking my pfp in the top right corner and selecting desktop view.
A few minutes later went to toggle back to mobile view and the drop down menu when clicking pfp in top right corner doesn't have an option for mobile view any longer so I'm stuck in desktop view.
Haven't yet cleared cache, I'm sure that would fix it. But the bug being lack of button should probably get addressed.
Cheers