Unannounced new game:
Superhero League of Hoboken

Unannounced new games:
Bad Dream: Fever
Bad Dream: Coma

I'm a little confused, you say these are unannounced but (for me at least) they clearly show as announced.

Announcement didn't go up until about 5 minutes after the OP.

Unannounced new games:
https://www.gog.com/game/strategic_command_classic_global_conflict
https://www.gog.com/game/strategic_command_classic_wwi
https://www.gog.com/game/strategic_command_wwii_war_in_europe
https://www.gog.com/game/strategic_command_wwii_world_at_war
https://www.gog.com/game/strategic_command_classic_wwii

It's your own topic, so of course you can do what you like...but might I suggest you adopt a "wait and see" rule? (As in: if a game shows up without an official announcement, wait an hour or two, or at least a half-hour; if no news post mentions the release within that time, post about it here.) I don't think a game appearing in the catalogue a few minutes before its attendant "Release" news post goes live should really be cause for posting here. I know the reason I created the "unnanounced promos" thread was to bring attention to discounts that GOG didn't seem to intend to mention at all, not to revel in catching them out by posting about it mere minutes before GOG staff did. I would have thought the goal of this topic was likewise to help the community, more than to try to "shame" GOG. (Yes, I know, "GOG should do it correctly themselves so I don't have to, they are so incompetent" etc., etc.) : )

These games look like they were made with the Civilization 2 scenario editor. That's not to say I don't like the look of them.

Anyone played?

Exactly. I mean, a game should normally be in the catalog before a news post appears, even if moments before, otherwise it'll just be a dead link. There have been a few titles, usually stuff like soundtracks or very minor DLCs, that they allowed to fly under the radar for longer, but minutes is normal and even up to a few hours shouldn't be a problem.

Unannounced new DLC:
Roger & James in They Came From Below (We Happy Few)

Now that seems pretty stupid not to annouce. Thanks you for doing this list!

Unannounced new DLC:
Lovecraft's Untold Stories OST

Unannounced game edition and DLC:
Whispers of a Machine Blue Edition
Whispers of a Machine Soundtrack

The official announcement mentioned nothing about them.
Blue Edition is listed as RELATED GAMES but you can't find Soundtrack anywhere on the announcement page.

Unannounced game edition and DLC:
Sigma Theory: Global Cold War - Deluxe Edition
Sigma Theory: Global Cold War - Original Soundtrack
Overcooked! 2 - Season Pass
Overcooked! 2 - Surf 'n' Turf
Overcooked! 2 - Too Many Cooks Pack
Overcooked! 2 - Campfire Cook Off!

The official announcement mentioned nothing about them.

Unannounced game demo:
https://www.gog.com/game/mutant_year_zero_road_to_eden_demo

GOG mentioned nothing about this.