Can't edit vertices in rounded shape I'm new to Blender and I'm fumbling around a lot with it. I created this shape from a cube I turned into a rounded shape by applying a Subdivision modifier. At first, I could see all its vertices, but somehow at some point, while I was editing it, its mesh became oversimplified to only a few vertices and now I'm only able to edit its extremities. How can I access the rest of its vertices?
Try turning off the On Cage option in the modifier. This will allow you to see exactly where the vertices are.
The image below was taken from Blender 2.8 so the icon is at the other end of the row to your image (2.9?) but it works the same.