I've got it!Short description:
First "Look at" application and transition time:
1. Right-click the mouse a little earlier choose Release, get a triangle - this is to regulate entry into the "Look at".
2. In the subsequent frames, set "Look at" the object you want.
Switch to another object (if there is one, or see the Finish immediately)
For a few frames before switching, make "Look at" the previous object. We get two triangles to regulate the transition section!
Finish the "Look at":
1. We release from "Look at" a place where the influence should end (and in fact the actor has long been looking the other way).
2. Go back a few frames back, copy and paste "Look at". We get two triangles to regulate the transition section!
And: In the timeline right click a look-at keyframe open transition curve presets to have custom motion between keyframes.
Many thanks to all for explanations and additions!
My short video about it:
My YouTube channel.