For what it's worth, the single-click-to-open nature of KDE means that when a new tab is opened (or takes focus) because of single-clicking on a file in Book Browser, the cursor is immediately going to the BV/CV editor and the TreeView items are losing focus as a result.
The only reason I've never noticed this behavior before whenever testing in KDE, is because turning off single-click-to-open is almost always the first thing I do on a KDE system. It's the only way I can keep my sanity.
