After the FF57 update I imported my configuration from FF56. I thought it was working fine, the URLs I had set up patterns for were being fetched through the specified proxy, or so I thought because the logs told me so. However this morning, I forgot to start Tor (the proxy I'm using), however all the URLs were being loaded, even the ones that were, according to the FoxyProxy log, loaded through the proxy. So it seems like it isn't working at all.

Great Add-on however! I understand the difficulties with porting the Add-on to WebExtensions and I am confident that the developer is capable of fixing this.