Okay... Thank you for telling me about your experience. I got where the confusing point is.

Maybe you've noticed it yourself now, Playground is only for organizing parts. I think it would be nice to have a Playground for the Memorizing part, but now it doesn't have that one... To make it appear there you have to put the content in the real Organizing part. Anyway, I found out that I need to make that part a little more understandable.