Using the Blend Shape Editor, you can set keys on all the target sliders at their current values, or key an individual target slider at its maximum influence value (1). Keying an individual target slider at 1 keys the influence of that target slider only, ignoring the possible blending influences of the other target sliders.
To key all target sliders
Maya sets keys for all the target sliders in the blend shape deformer.
To key the maximum influence of one target slider
Maya sets a key for that target slider only, ignoring the possible blending influences of the other target sliders.