OK, those aren't tabs — they're context-menu options.
Zotero 7 is based on a newer framework that tries to follow newer Windows design conventions, such as from Windows 11. You'll see the same menus in Firefox, and you'll see similar menus in stock apps (File Explorer, Edge) on Windows 11. (Really, Zotero's should use larger text to better match those, but the spacing is similar.)
zotero 6: https://img1.imgtp.com/2023/05/30/8SfkATt0.png
zotero 7: https://img1.imgtp.com/2023/05/30/HUnnz9oo.png
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zotero 6 can show full the items that takes up very little interface space, but zotero 7 even needs to scroll down to show all the items.
Zotero 7 is based on a newer framework that tries to follow newer Windows design conventions, such as from Windows 11. You'll see the same menus in Firefox, and you'll see similar menus in stock apps (File Explorer, Edge) on Windows 11. (Really, Zotero's should use larger text to better match those, but the spacing is similar.)