As a side note, to show of me stupid and GALAXY-Client Dev stupid:

Somehow "-skiphidden (skip games marked as hidden)" in my "gogrepoc.py update" batchfile did only filter

A.D.2044

but not all other games which i did "hide" in the GALAXY-Client:

alders_blood_prologue
builders_of_egypt_prologue
cdpr_goodie_pack_content
chuchel_botanicula_goodie_pack
cyberpunk_2077_goodies_collection
hedon_demo
hello_neighbor_demo
legend_of_keepers_prologue
overload_playable_teaser
sunrider_mask_of_arcadius

I had to manually edit the *.dat every damn time when i updated it to delete that games from there.

I was on the verge to throw a tantrum BUT i did check then directly my library on the WEBPAGE without the CLIENT and io and beholde:
Only the A.D.2044 was flagged.
After manually flagging the other 10 ones LIKE I ALREADY DID IN THE GALAXY-CLIENT the script did now recognize the hidden games.

I think the GALAXY-Client only flags its TAGs and so on at the client side and not at the server side...

So learn from an idiot like me: Hide your games one the Webpage of the GoG-Server and not locally in the GALAXY-Client and do not trust the GALAXY-Devs to do shit in the correct way.

Also Galaxy ignores the hidden tag from the servers. I have hidden all my demos for example and Galaxy keeps showing them.

I have never used hiding on the Galaxy client so I'll have to look into this, It's possible it sets a tag that I can still access and respect.