Hello,

is there a way to access custom maps on the GOG version of the game ?

Yes - https://steamworkshopdownloader.io/

How to use Steam workshop levels with the GOG version:

1) Find the map(s) you want on Steam
2) Download the map(s) with this Steam Workshop Downloader .
3) Navigate to this folder on your PC: C:\Users\[Your Username Here]\AppData\Local\ThankYouVeryCool\Saved\SaveGames\levels\
4) Make a folder that matches the name of the map exactly, place contents of zip inside the folder

Thank you!
I noticed the funny binary names in the game :-) And I neglected to search for them in the user folder.
Works fine.

For anyone who has followed the link above you should have found that it is NO LONGER
available or active for our use. Valve/STEAM has stuck it to these folks butt good...

It is a real shame because the way Valve did this they have made it legal to "STEAL" any
file uploaded to their workshop storage so THEY have final distribution rights to them. IE:
Licensed Product of STEAM/Valve..

Perhaps GOG needs to look into offering a mods source of their own for free game mods to
provide us with options we would have elsewhere? Just an idea to bounce around?

Alternatives to Steam Workshop exist, such as mod.io, but developers and publishers need to express interest in them.

That is so true Plok_HR. I found a way, using the demo of the game, to access the work shop files
so right now I am looking at "subscribing" to them then copying them to a separate folder like I do
with all of my workshop game mods since STEAM is known for removing them from the workshop
AND user folders if left in original format. There are a number of workshop mods for the Haydees
and ARK that I saved and it's a good thing I did because over the past year Valve/STEAM has been
purging "Older" workshop mods as "possibly" no longer compatible with the game version. As yet I've
only found this to apply to the external source from EEK.games for House Party because of changes
the game engine AND a number of other files at the behest of STEAM/Valve. Earlier versions of the
game could be launched WITHOUT STEAM running. Valve/STEAM did not like this because they'd
lost control of the game files.

Too many greedy gremlins in the house!