I have tested this and I am very pleased.
The normal admin menu is now gone, but like the mobile foldout.
I have @ _adminNav-hideWidth: @ xf-responsiveWide; to
@_adminNav-hideWidth: 20000px; set.
And I use the addon from @ozzy47 to keep the additional admin menu always up
Now it is much easier to edit templates because on my tablet in visibility more space.
Too bad that this setting is not part of the core.