I did not know about the Product Library function in SNAP, so I have not used it.
I download most of my Sentinel-1 data from the ASF mirror archive with their Vertex search GUI or through their API. The ASF API and clients have efficient systems for bulk downloads. Downloads are much faster from ASF than from the Science Hub since I am in the USA. If I need a very recent scene that is not yet copied to ASF, then I use the Science Hub search to find and download data.