You read that correctly—indexes can now be made invisible in MySQL 8.0!
From a performance or optimization point of view, this new MySQL 8.0 option is appreciated because you can essentially disable an index before deleting it. When you create an invisible index, it is always maintained normally, but the optimizer will not see it.
In other words, if you're not sure whether you need an index, you can mark it as invisible and the MySQL optimizer will not use it. After monitoring your server and monitoring performance, you can decide to reactivate it if you think that will result in improved performance.
As you probably already know, when the query optimizer can find an action plan to exploit them to their fullest, indexes can be of great assistance. They reduce execution time and improve the performance of your queries. However...