If you search for an album, get results, then right click any track then Download Folder(s), it works.
But there is a case where this feature never works (on Mac): you search for a track, get results, then if you right click that single track/file and Download Folder(s), in order to get the full album or compilation, it does not work and you'll only dl that single file, not the folder containing it. This is very annoying. The only turnaround for me was to right click the track then Browse Folder, then, once inside the user's folder, use Download Folder(s).
The build I was using was almost a year old, and I just downloaded the latest build, and it adds a new layer of frustration: Browse Folder is gone. And this is stupid because while Browse folder would send you directly to the specific folder containing that single track, Browse user's files sends you at the root of the user's folders, and you have to navigate trough his (more than often messy) files to get to the folder.
I hope this gets fixed soon by a dev who actually uses slsk (I can't believe that a regular user would go backwards like this).