Thank you for your feedback! As for switching the current course, Duolingo Boost does it "automatically", however data are refreshed only once in 5 minutes, therefore it may take a while before you see the actual data like your current course. I know this it not an optimal solution and I'm thinking about how to make it more responsive without making too many requests to Duolingo servers.

Personal dictionary seems like an interesting feature, I'll look into it. Meanwhile, there already is a feature called "custom lesson notes" which allows you to write your custom notes in every "tips" section (in the sidebar).