Search for category in Create Post page

Hi there. I am sure I saw it already but now in WP 4.0 it seems to be gone!

What I want is simply search through my categories when I create a new post. On the right hand side there’s this nice box with the list of categories, tab for most popular categories and link to add new category. But I have 150 categories and it would be way easier if I can filter them out when I add new content.

Does anyone have an idea how to do it? Either codewise or plugin?