This module is designed to test the development of hook_toolbar() and hook_toolbar_alter() in #1847198: Update the structure returned by hook_toolbar(). (You should apply the latest patch from that issue before installing this module.) It should also serve as a basis of the API documentation in toolbar.api.php and additional tests for #1839514: Establish test coverage for toolbar module..
I would like to have a co-maintainer who can be responsible for the CSS and (especially) javascript aspects of the D8 responsive toolbar.
When this module is ready, I plan to submit it to the Examples project rather than promote it to full project status.
Update:
There are now competing patches on #1847198: Update the structure returned by hook_toolbar(). I have added git tags patch-17 and patch-38 to this project corresponding to the patches attached to the corresponding comments on that issue.