Pre-requisite: a compatible browser with a compatible script engine. It has been tested for Firefox with Greasemonkey, and Chrome with Tampermonkey. It has been tested with these configurations, but it's also reported to work with Opera.

Installation: you can download the script by clicking the following link and your browser will ask for your confirmation before completing installation. Here it is: swwf.user.js (current version is 0.3.3, released on April 14 2018).
If your browser displays an error message, or shows script code in a blank page, then you probably missed the script engine installation. Please go to previous step and make sure your Greasemonkey or Tampermonkey is properly installed.

Usage: main: you should see a new set of entries in the left menu on your whitelist management page and on your blacklist management page, as shown in the screenshots below:

Whitelist page new menu:	Blacklist page new menu:

Usage: whitelist wishlist: the script reads your whitelist and sends it to this server. After a bit of work from the different scripts involved, you will be redirected to a page hosted on this server and displaying the wishlist games from your whitelist.

Usage: export whitelist / blacklist: the script will work a little bit and generate a big line of text. You can store it anywhere you want (copy/paste in text file, e-mail, anything) and use it later.

Usage: import whitelist / blacklist: if you have made an export with the previous function, you can use this line of text to make the script add all these users again to your whitelist or blacklist. Just copy the saved line in your clipboard and paste it when the script asks for it after clicking on the required link.

Usage: empty whitelist / blacklist: simple function that will remove everyone from your whitelist or blacklist.

How does the whitelist wishlist work ?: First, it reads your SG whitelist and opens (silently) every user's profile page to get their Steam ID. Next, it sends those IDs to this server, so it can read wishlists from Steam. Final step is the display of the result of this work. For better performance, the wishlist games displayed are now limited to top 100 by default (you have alternative options, at the top of the list of games, to display top 200, 300, 400, or all the results). If your browser supports it, the SG names / Steam IDs pairs are now stored by it internally so the script don't need to open the user page each time. Last but not least: server refreshes steam wishlists on a daily basis for all users who have been used in a whitelist wishlist in the previous 30 days. Trust me when I say it makes things way faster :)

I found a bug, what to do ?: You can drop a line in the SG forum thread for this script. Please remember that since it works by reading HTML pages, it can stop working properly anytime without notice (in case Steamgifts or Steam change their HTML layout, or in case this server goes down, or anything else). In such case, I'll be happy to fix it if someone makes me aware of the problem.

Who made that ?: me :-) Also a few lines of code are coming from other scripts made by Psycho345 and BarefootMonkey. I want also to thank HiroHiro who made serious testing with the first prototype :)