New keyframe affects all

[Andy Neil]

I think I understand you now. You’re spending a lot of time trying to get Motion to behave like Flash when Motion can actually do the things you want much easier and quicker than Flash.

You can do your Fade In with a behavior instead of keyframes. Just select the layer and click Add Behavior/Basic Motion/Fade In-Out. Adjust the fade out slider to 0 and the fade in slider to whatever you want.

To lengthen or shorten a layer, you can place the playhead wherever in the timeline you wish the layer to end up and hit O on the keyboard to lengthen/shorten the OUT point of the clip. Or I to lengthen/shorten the IN point of a clip.

In addition, you can open the Timing Pane (F6), select as many layers as you want, and drag the ends to lengthen/shorten those layers relative to each other.

There are many other means by which to manipulate the position of layers in the timeline, which you should be able to find in the manual. But those relate to the example you give above.

Andy

https://www.timesavertutorials.com