You have a checkbox for “Visible,” which when checked makes something visible in the editor. This makes sense, checked = true/yes unchecked = false/no.
Then right under that you have “Hidden in Game,” which when checked has the opposite effect of hiding something in the game. This is counter intuitive and sometimes makes you have to stop and think about it because you have to remember that ticked (true/yes) is to hide it, not to show it. The C++ function of SetHiddenInGame() is equally counter intuitive as you are setting it to true to hide instead of true to show. Hide is naturally a negative term that relates well to false/no, while show is naturally a positive terms that relates well to true/yes.
It would be nice to see this terminology reversed, and then just reverse the ticks on all objects when the editor upgrades a project.