NEW header at minimal size - visual proposal ( UPDATED, Agust 20 )

<h1>1. Premise</h1>

<h1>2. Proposal detail</h1>

This can work with two forms:

1. minimal size with header to preserve some menus or buttoms.

2. add an extra minimal size occlude the header when no need or when i want collapsed vertical window.

<h1>**PLUS:</h1> But when work with two or more 3D windows, all windows load all models and viewport it is slow

with an extra minimal size even if possible the window would can be like to if not been enabled, it not load models in memory but yes the window config, display options, shading, clip, etc.

**NOTE: in Blender 2.8 only form to collapsed headers is manually with toggle header option, no shorcut, no drag.