Then it's meaningless.
If it's not in Scripture, it's not infallible. It's merely the opinion of men.
I really don't care much what a bunch of corrupt, immoral, charlatans who claimed some sort of special spiritual insight due to the positions they awarded themselves thought.
The actions and behavior of the Catholic church for the majority of its history shows a dearth of spiritual insight and leading.
They ought to just hang a sign above the door of the Vatican that says *Ichabod*. There is no godliness there.
When they can get their act together and start acting like the Christ they claim to represent, then they'll gain some credibility and might have something worth saying and listening to.
But until they clean house and do it publicly and decisively, they have nothing to say.
“Sure I can, because it is a knowledge possessed by the Church, which is not expressed in the scripture.”
Where did this “knowledge” come from? I ask. And When?
This is the heresy of Gnosticism. One of the primary beliefs in Gnosticism was the possession of "secret knowledge" by the chosen few. It would be good to repent of it.
Says who? Besides, there are facts that are true historical facts not inthe scripture. The assassination of Julius Caesar, for example, is not in the scripture, but it did happen.
When they can get their act together and start acting like the Christ they claim to represent, then they'll gain some credibility
So you don't believe the Church. You are free to do so. However, the behavior of some members of the Church, -- some as awful and un-Christlike as to leave the Church altogether! -- has no bearing on her witness to particulars of the life of Virgin Mother Mary 2,000 years ago.