Use Soft Select

Keys menu

Use Soft Select

When on, Use Soft Select affects keys adjacent to a selection set of keys according to a falloff threshold. This applies to both Curve Editor keys and Dope Sheet Edit Keys modes.

To adjust the Soft Selection range and falloff, choose Soft Select Settings on the Keys menu.

TipKeys are “soft-selected” across time only (horizontally).

Procedures

To soft select keys in Track View:

In either Dope Sheet Edit Keys mode or in the Curve Editor, select a single key in the middle of the animation curve or graph.
From the Keys menu, choose Use Soft Select.
From the Keys menu, choose Soft Select Settings
The Soft Selection Settings dialog appears.
Change the Range and observe the soft selection display in the key window.