This is awesome to see, thank you! There's a couple problems that need to be sorted out in this initial version:

1. There's an out of place "line" running through the interface, this is the line that is underneath the original "title bar". I think you may have accidentally left it in:

To fix this, you can replace line 98 with ZO_SharedTitleDivider:SetHidden(true)

2. The "title bar" isn't matching the styling of the rest of perfectpixel:
Your Addon:


Correct Example:


3. Some tabs are missing their titles altogether, such as the "Item Set Browser" menu.:

I can see why this is an issue, the original extended journal addons use a different way of formatting the titles where there's a big title on the left, and only a subtitle where there needs to be. Instead, what I suggest you do is just use the titles from the tooltips and have one present for every tab, so for example, "Loot Log: History", "Loot Log: Materials", "Item Set Browser", etc.

4. The Crown Store is messed up:


Other than that, it's looking great so far!