unable to force JS library to HEAD I've read the main docs about this but find it lacking context. This did better job of explaining and it seems it should work. How to force a JavaScript library to load in the &lt;head&gt; of a Drupal 8 page 
EVERY attempt I try returns 

A colon cannot be used in an unquoted mapping value


Searching for this, I've attempted to enclose the include line in single quotes, without, but all within context of attempting 
js-header

Since this YML, I'm making sure we're using two spaces for indentation and nothing else. What am I overlooking here? This is a snippet of mytheme.libraries.yml

  flexslider:
  version: 1.x
  css:
    theme:
      includes/flexslider/css/flexslider.css: {}
  js:
    includes/flexslider/js/jquery.flexslider-min.js: {}
  dependencies:
    - core/jquery

fontawesome:
  version: 1.x
  css:
    theme:
      includes/fontawesome/css/font-awesome.css: {}

global-styling:
  version: 1.3.2
  css:
    theme:
      includes/mapquest/css/mapquest.css: {}
  js-header:
    header: true
      js:
        includes/mapquest/js/mapquest.js: {}


This is portion of mytheme.info.yml that applies:

  #Libraries
  libraries:
  - mytheme/bootstrap
  - mytheme/flexslider
  - mytheme/fontawesome
  - mytheme/global-components
  - mytheme/global-styling
I think you've indented too far. The line following header: true is directly beneath it in the example you linked to.

global-styling:
  version: 1.3.2
  css:
    theme:
      includes/mapquest/css/mapquest.css: {}
js-header:
  header: true
  js:
    includes/mapquest/js/mapquest.js: {}