Up until the most recent release (53.0 from April 17 2017) I was able to manage screen orientation by adding "app.orientation.default" with type string, value "landscape" to about:config. This locked Firefox in landscape mode, regardless of global auto-orientation enabled or disabled. With the latest update to FF this functionality broke, as it was broken in FF Beta for some time. I want to be able to control this behavior besides global auto-orientation - which is annoying, confusing, takes time for rotation animations, and requires additional attention to the way your wrist is positioned, to prevent sudden jumps. Needless to say, this option is always off for me.