You can create a feature line from an alignment, and use this feature line to grade from the alignment geometry.
You can also create a link from the feature line to the alignment so that it updates dynamically if the alignment is edited. If the feature line is linked to the alignment, you cannot edit it directly.
However, it updates automatically when you make edits to the alignment or its profile. These edits also update any gradings attached to the feature line. If the feature line is not dynamically linked, it does not maintain its relationship with the alignment and you can edit it.
You can specify the CreateFeatureLineFromAlign command settings prior to creating feature lines.