Filter Tools Properties 
Filter Tools will filter all the tools that are available in the Anim Tools Panel that can change the keyframe values. It's possible to filter.
- W X Y Z attributes from all the transform channels.
- Channels of Custom Properties
- Only selected keyframes.
When using the filters The Filter button will show the initial letters of the channels that are currently being filtered, L for location, R for Rotation and S for Scale.
This is a reminder for the user which channels are currently being filtered.