It seems that the so called "vertex crease" weights (see: https://graphics.pixar.com/opensubdiv/docs/using_osd_hbr.html#vertex-creases, I think a better name would be "corner" weights) are currently not implemented but will be in a later version of Blender as discussed here: https://blenderartists.org/t/blender-3-0-opensubdiv-development/1311217

It seems that the so called "vertex crease" weights (see: https://graphics.pixar.com/opensubdiv/docs/using_osd_hbr.html#vertex-creases, I think a better name would be "corner" weights) are currently not implemented but will be in a later version of Blender as discussed here: https://blenderartists.org/t/blender-3-0-opensubdiv-development/1311217

Edit: Beginning with Blender 3.1 this feature is now available: