In my animation, I am using the red button to automatically insert key frames. So, it automatically saves Rot/scale and location. However, suppose that I need to just save the rotation of the object, so I click I and to choose Rotation and I expect that in the dopesheet the LocRotScale will be changed to Rot only, but it does not change. I know that I can turn off the red button and insert key frames with rotation only. However, I see a lot of tutorials that use the red button and I to insert key frames but I do not understand its utility? Any explanation will be appreciated.
The red button in the timeline enables the Auto Keyframe function.
By default, autokeyframe will create a LocRotScale keyset. So even if you changed only one thing and left the rest untouched, it will create 9 keyframes, one for each axis of the Location, Rotation and Scale.
If you only want to record a specific channel with autokeyframe (for example rotation, but not Location or Scale) you can create a different keyset by left clicking here:
And enabling "use Active Keying Set Only"
Your changes will only be recorded for the current Keying set.
You can temporarily disable the use of "Active Keying Set Only" and make changes in other channels (like location for example) and the autokeyframe will revert to the default behavior of recording LocRotScale.
SOLUTION: If you only want 1 key (loc, rot, or scale) and not all of them you must first record your motion and then go into graph editor and delete the keys you don't want. For example, if I want to move and rotate a hand, I can't do both at once while recording. So I start by rotating it so it waves. The auto-keyframe button records all keys and not just rotation, so if I try to record location afterwards, it's going to jump and glitch all over because its location was originally keyframed when I rotated it. So I go into graph editor and delete the XYZ location keyframes. That way I can record location without the buggyness. Hope this helps. ;)