Since this version does not include the launcher, how are we supposed to modify settings like anisotropic filtering, parallax occlusion, tessellation, etc?
Is there any way to find the launcher or was it removed alltogether?
Thanks.

the best solution here would be to hit the uninstall button, and then get the Dark Mod.

that is the true successor to the Thief trilogy.

Haha, snarky answer but the correct one, in a way.

To give you an actual answer to your question, the GOG shortcut that launches the game has the -nolauncher argument, which stops the launcher from opening. Remove this from the shortcut to get access to the launcher again.

Edit: Or run Shipping-ThiefGame.exe directly from <game path>\Binaries2\Win64