For more than 30 years I never had a squeak or a creak caused by my saddle, until recently. The root cause turned out to be a classic case of unintentional results.
I had an annoying creak in my bike that I couldn’t pinpoint, but after a couple of months finally discovered to be a loose front quick release. During that time I added oil to just about every part of the bike, including the seat rails.
This is one place where you should never add oil, I discovered the hard way. Fine dirt and grit kicked up by the rear wheel clung to the oil on the rails and eventually worked its way down into the rail bed.
It was the perfect recipe for saddle creak. I took off the saddle and removed all signs of oil and dirt from the rails and post. That fixed the problem. You may want to grease the seat post bolt, but that’s the only place that needs it.
I’m not saying this is the cause of your problem. But try cleaning the rails before moving on to the next possibility.