I'm may be completely blind, but I can't find the dam "more" button in my GOG Galaxy.
Is this realy available in the client 2.0?
I have a similar problem as descripted here: https://www.gog.com/forum/general_beta_gog_galaxy_2.0/possible_issue_with_multiple_launch_options
You are not alone. I am also struggling to locate this mysterious "more" -button for this game in GOG 2.0..
I have a small workaround for now:
You can add the add-on manually by searching for it under the options menu of gog (gear symbol on the upper left -> add games and friends (or something like that). Then search by typing the game, and select it with the arrow keys, and on the top of the menu you can add the game as owned. Then link the game with the .exe file. If the game does not exist in the database, you can add a random one and change the title and icons later.