I wouldn't worry about that area. As long as it does have a shallow area for frogs and newts to enter they will probably use it. Having one area in the pond with a steep slope won't bother them as they as they can get in and out from another section of the pond.
If anything, it might be beneficial for the frogs to have a deep section where herons and other predators cannot easily access them.
If you are worried about rodents, shrews, moles, or hedgehogs falling in, then just make sure that they can swim to a more shallow section to climb out. Animals don't just fall in the water and drown. Almost all animals can and will swim and they only drown because they are trapped.
We don't have hedgehogs in the US, but we used to have moles, mice, and chipmunks fall into our swimming pool back at our old house in Connecticut. They undoubtedly could not escape the slippery, vertical walls of the pool. We even had amphibians drown in there.
It was a death trap for insects, spiders, amphibians, and the occasional mammal. Gradual slopes prevent animals from falling in, but they also allow animals to escape even if they fall into a steep section.
If you desire, however, you can add rocks and a few logs or add sand or gravel to make the edge less steep.