First make sure the target (other) track has the same automation envelopes on it as the source track. For example, if you have Volume and Pan automation on the original and you want to copy a chunk from both of those over to the target track, you need to add (empty) Volume and Pan lanes to the target track first.
Then you can select and copy/paste or drag-move to the target track.
P.S. It's more... predictable... if you unfold all the automations into their own lanes below the tracks. Both source and target. Then you can drag-select across all the lanes you want to copy, then click and hold the selection until it turns into a "move" shape, then drag it onto the same lanes under the target track. Hope that makes sense. And if you're trying to select and copy multiple lanes in one go to a different track, you'll need to make sure the lanes are in the same order underneath each track. Play with it a bit and you'll see.
