Edit screen

This configures the animation.

Playback Controls

See Playback

Animation Name

You can rename the current animation by changing the content of this textbox (Anim 1 in the screenshot)

Change Length Mode

This allows resizing the current animation:

Length Locked: Default settings, locks the animation length to avoid surprises.
Crop/Extend End: Moves the last keyframe; if resizing smaller than the animation length, will delete keyframes.
Add Keyframe End: Adds a new keyframe after the last one. Only allows extending the animation length.
Crop/Extend Begin: Moves the first keyframe; if resizing smaller than the animation length, will delete keyframes.
Add Keyframe Begin: Adds a new keyframe before the first one. Only allows extending the animation length.
Crop/Extend At Time: Extends the current curve (between keyframes), pushing back all keyframes after it.
Stretch: Extends all keyframe duration, effectively changing the speed of the animation.
Loop (Extend): Adds keyframes by repeating the first ones, looping the animation.

Animation Length

Based on the Change Length Mode option, change the animation length in seconds.

Loop

Whether the animation should loop. When looping, the last keyframe becomes non-editable, since it will automatically be the same as the first frame.

Ensure Quaternion Continuity

Quaternions represent an "application of a rotation", not a "value of rotation", which is a good thing usually but can give surprising results when animating. Unity3D provides a built-in solution to avoid weird effect, which are well explained in this forum post.

Auto Play On Load

When loading the scene, if enabled, the animation will start playing immediately.

Next Animation

After the current animation is complete, which animation to play next.

Next Blend After Seconds

After how much time should the Next Animation play. For looping animations this can be any value, for non-looping animations this cannot be changed and will automatically be the animation length minus the blend duration.

Loop

Whether the animation should loop. When looping, the last keyframe becomes non-editable, since it will automatically be the same as the first frame.

Transition (Sync First/Last Frames)

Sometimes you may want to create non looping animations to transition between two loops. This usually requires keeping the first frame synchronized with the last frame of the previous animation, and the last frame synchronized with the first frame of the next animation. When this option is enabled, these frames will always be synchronized automatically, so you only have to create the intermediate keyframes.