I'm using V7 Bookmarks (Version 4.8.0) with opera (Version:73.0.3856.257) on a linux system (arch).
Sidebar is configured as permanently visible.
Opera is loosing the V7 bookmark content all the time after some minutes and shows a blank sidebar. Till now, I couldn't figure out a systematic on that behaviour. After using reload botton, I see them again and its ok for a while.