Currently, I am waiting for GOG to send me some information on a URL/API to manually, write an import script. In the meantime, I wrote a quick and dirty script that helps with this process.

HOW IT WORKS
It is very simple: You create a game list and save it in a text file called "steamlist.txt" (can be a game list from anywhere)
The app will run through line by line of this text file, converting the naming convention of spaces " " to "_", then open a tab in firefox (sorry I only work with firefox, but can mod the app to accept any browser) with the results. It will either have a page description where you can click "wishlist" or a generic GOG game list (search failed). It does this in groups of 20 tabs.
You can quit any time and resume your list at a later time.

Is this perfect NOT? It just automates some boring steps of searching. Both steam and GOG give different names to the same game. The app does not recognize that. However, my 1,176 game list, found about 90% of the games that steam and GOG had.

Also, keep in mind, GOG library is not as big as steam, and the age of the game (when it was released) is vastly different, so on large steam lists, you will most likely get tons of failed searches.

There is another link here (https://www.gog.com/forum/general/how_to_transfer_large_steam_wishlist_to_gog_wishlist) that uses a different method for more advanced users for importing games to the wish list. Looks promising, I used to program in AutoIt, however, I wanted something simple.

Download from from Mediafire includes QB64 source
https://www.mediafire.com/file/rrsr27z2va6zyhs/gogimport.zip/file

TEST RESULTS
I was able to import my 1k game list in a little over an hour. It is not automatic. here are some useful steps to make this faster:

TIPS FOR FASTER ADDING TO WISHLIST
[olist]
[*] Load up the app
[*] Enter 0 (zero) if it is your first time, or enter the line number left off at - i.e. you ran this and got 46 games installed, you would put 46 or 47 here so it can continue in the list
[*] The app will open up 21 TABS in firefox that have the search results of each game - if available on GOG
[*] If your game comes up - WISHLIST the press CTRL-W
[*] If no game - just the standard GOG game list - just press CTRL-W
[*] The next tab will be visible - repeat steps #4 and #5
[*] After all your search tabs are closed, ALT-TAB press enter on the app, and it starts over with the next 20 games in the list
[/olist]

As you can see, this just eliminates manually comparing steam games with GOG games, search for it, then clicking WISHLIST.

Again, not fast, but hopefully if several of us keep making crazy "import" apps, GOG might take over. In the meantime, hopefully GOG will offer me a solution where I can write a real app that imports instantly.

I would love to see any modifications to the app. I wrote it in 15min. just something quick - it definitely can be improved on!!

Cheers.

OK, so support was able to help with some API descriptions. Easy script to write. One HUGE problem. The naming conventions. Both steam (and others) have different ways of saving game names.

Example:
Steam: ARX FATALIS
GOG: ARX

This would not yield a match, and your wishlist compare would skip this game. There are more elaborate names as well.

I went through my 1,100+ games and only about 40% made it through, and most of those were single names

I found a semi-full list of gog games, might take a look to see if there is a way to do a kludgy compare.

I'll keep tinkering LOL!!!

+1 Thanks for sharing :)