I'm really embarrassed about this... I certainly USED to know how to do it... and I've searched for the answer, and I thought it was going to be easy to find, and it wasn't...
Anyway. I need to edit a layer's OUT point without affecting the location of the IN point in the composition. [ is working fine for the in point. Then, pressing ]... The entire layer slides to the left so that the out point is there, all right, but the in point has now moved the other way so that it's gone back in time. I want the out point to TRIM the (text) layer and make it shorter, not slide it around so that it's the same length and all it's done is to move.
The text layers will overlap each other, but the thing is that they're of varying lengths
(It's AE 5.1, btw...)
I just KNOW there's an easy way to do this. And everyone here is so smart! 