How do I bring back the little menu under the main window? So I'm working in Blender and I've just learned how to use shape keys through this awesome tutorial:
https://www.youtube.com/watch?v=T1KntZJCFUo

Except now that really helpful menu section(highlighted in red in the screenshot) is now gone and I don't know how to bring it back. I'm getting better with Blender but I would still count myself as a beginner/learner, so any advice would be greatly appreciated :)
Near the upper and right corner of the red box in your 2nd image there is a small + click it and the small section will restore ;).