Set custom sort order for index pages in the CP? Good chance this is more of a feature request than a question you can help out. But as I am new to Craft plugin development and might oversee something I ask it anyways:

Now that it is possible to customize the index pages in the CP using the plugin hooks modifyEntryTableAttributes and getEntryTableAttributeHtml, what do I have to do to make my custom columns appear in the sort order dropdown / make the entries sortable by my new columns?
You weren’t overlooking anything, we were :)

We just released Craft 2.3.2616 with four new hooks:


modifyEntrySortableAttributes
modifyCategorySortableAttributes
modifyAssetSortableAttributes
modifyUserSortableAttributes


That should do the trick for you.