you dont have to indiviually change them, in the editor select all the hidden actors and in the details you can set visible (untick)
or same method select them all and give them the same tag (in editor)
then in blueprint in game you can select all the actors with that tag and set visible to false
Just to add a little visual to what High500 was saying:
Highlight the ones you want, go to the “Rendering” or “All” tab of the details window, and tick “Actor Hidden in Game”