add keyframes directly on yellow line in camerapreview.
Makes keyframe process easier.

Just go to the position you need a keyframe and hit the key 1, this will set the keyframe. The thing wilt the "yellow line" is, that the keyframe doesn't only apply to that line, it applies to all other lines too. So if you have the "All" togglebutton toggled, then you will see a variety of curves. Also you can select the curve in the dropdown that you want displayed. Any regular Keyframe (except for the crop keyframes and the HG Keyframes) will apply to all edit curves.