As far as I can tell with my Singer 533, there is no way to drop the feed dogs. The manual says that you have to get a different needle plate that covers them if you want to do free-motion sewing.
But, I haven't been able to locate one of those either.
But, I haven't been able to locate one of those either.
There is a dial on the top of the machine that goes from "D" and then to numbers. This increases the pressure of the feed dogs. The "D" is for darn and it allows you to move fabric freely.