Latest Hookmark version (Version 6.9 (6231; Integration v. 362) is showing one of my pinned item and an empty list in the bookmark view. Restarting the app fixes the view state (the pin is coming from sync with another machine).
On the machine where I pinned this item (and another has not synchronized after several minutes, but let’s take this one bug at a time maybe), the view does not show any pinned items neither. Restarting the app there also fixes the view state.