Hello Jon,
This is not handled via Kentico API but via JavaScript. You can see that also when you will inspect any element from the Content tree:
<span class="ContentTreeItem" onclick=" SelectNode(85, this); return false;">
<i class="icon-doc icon-doctype" aria-hidden="true"></i> ...
And the method SelectNode from \CMSModules\Content\CMSDesk\Content.js file is called which could be located on the line 342:
// Select node action
function SelectNode(nodeId, nodeElem, tab) { ... }
Best regards, Martin