Use options in Key Controls window to perform all keyframe-related tasks in your animations including creating, deleting, editing as well as selecting tangent and interpolation modes.
The Key Controls is displayed by default in the Editing layout. If it is not displayed, you can access by selecting Window > Key Controls from the menu bar.
You can access the Key Controls window at any time via the menu bar by selecting Window 
Key Controls.
The Key Controls window includes menus and options that let you do the following:
- Set and delete keyframes. See Setting a keyframe and Deleting keyframes and keyframe regions.
- Selecting an interpolation mode
- step through keyframes
- create and select animation layers
- select keying groups
- set tangent and interpolation modes
- plot or clear animation
Once you have modified a selected object’s properties, the Key Controls window lets you set different types of keyframes manually. You can also activate the Auto Key option to set keyframes automatically every time you change a selected object’s properties. Multi-Referential constraint settings