It's not a problem of the specific website. I installed Portfolio+ 2.4.8 on another Joomla website and the settings of lightbox are also not available. It seems that it's a problem of installing version 2.4.8 for the first time.
In which table of MySQL database are these settings stored? I need only one fix to disable Lightbox in all portfolios of the website.
I could not create a ticket because Google mail is refusing my email.