Collapsible sidebar

Seeing a collapsible sidebar just makes me fear for all those less tech savvy users who accidentally collapse it once and spend the rest of their time with the interface squinting at the inscrutable icons that remain. Of course there are many ways that the chances and repercussions of this can be mitigated, the question is when is the extra screen space worth the trade off in complexity

Here is my crack at it, who knows if I'll ever actually use it.