Thanks, got it. The one at top right was so obvious that I didn't look further. Left-clicking (not d-clicking) that opens the 'Search Forums' dialog, as does using 'Advanced '.
Re DRM:
Although an experienced end user I'm neither programmer nor github techie. My 400 or so Amazon UK Kindle purchases over the years includes one I'd have liked to convert to EPUB for a friend. But despite methodically following a variety of the posts here I'm still unable to achieve that. I think I'll cut my losses and give in.