Sometimes the plugin works, sometimes not

The button should appear above the content editor:

http://i.imgur.com/PPusqVd.png

If it appears intermittently, there might be a network issue or another local problem. Try removing the temporary files of your browser.

You can sort the content blocks alphabetically on this page by clicking on ‘Title’. It is not possible to do this from the insert content block popup.

I *think* I now understand what you mean, would like to alphabetically order the custom posts in the select box on the popup:

http://i.imgur.com/mLdUB8V.png?1

This is not something I am planning to add. If you really need this, you can easily modify line 51 of the plugin file popup.php and replace it with this:

$args = array( 'post_type' => 'content_block', 'suppress_filters' => 0, 'numberposts' => -1, 'order' => 'ASC', 'orderby' => 'title' );