Hey I just found a couple problems with your addon if you'd be interested in fixing them:

1. Your addon is missing the "menu blur effect" as described in this post. Every other menu has this blur effect except for when using your addon. I'm not necessarily a fan of the blur effect itself, but it's a bit jarring how every other menu has it except yours.
2. There is a slight "flash" that can be observed when switching from the quest journal tab to any other tab in the journal. Switching to the quest journal is fine. It's only when switching from the quest journal tab to another tab.