When adding a shape key, set its blend value to 1.0 / 100%.
There is no practical use case where user wants to add shape key but
not work on it. New shape keys at value 0 have no purpose. Adding
shape key should be interpreted by Blender as user wanting to
sculpt/model on it. Also, being at 1.0 initially doesn't change
anything visually, because key isn't edited yet and it doesn't deform
mesh.
The default value of the shape key is also set to 1.0. When using
right-click to reset values, user most often wants to return to 1
(which is "correct" state of deformation without multiplication)
rather than 0 (which is no deformation at all).
Co-authored-by: Sybren A. Stüvel <sybren@blender.org>
Pull Request: https://projects.blender.org/blender/blender/pulls/133399
7158e02aed