When working with the timeshift tool it would be beneficial to show what the tool has selected.
For example, if you have multiple clips in a track that are next to each other and you try to use the time shift tool, nothing moves and there is no indication as to why. A visual indication that only one clip is selected would at least provide some feedback as to why what the user is trying to do isn’t working.
It works the other way round.
If there is no “selection” (see: Selecting Audio - Audacity Manual) then the Time Shift Tool moves only the audio clip that you click and drag.
If there is an audio selection, and you click within the selection on an audio clip, then all audio clips that are included, or partially included in that selection, will be moved.
Then I think it would make more sense to show the clip as being selected.
For example, create a clip of audio 15 seconds long.
Create cuts (Ctrl + I) at 5 and 10 seconds so you have 3x 5 second clips.
Now realize that you needed to add something at the 5 second mark. After you shift to the time shift tool and click on the middle clip (the one ranging from :05 to :10) and it won’t move.
If you zoom out far enough you can shift your current clip past the next clip, but I have to imagine that the more common workflow would be to nudge the rest of the clips rather than be able to drag one past the other.
When you have that middle clip selected there is no indication as to why nothing is moving. Visual feedback of just that one clip being selected would at least give you some indication as to what is going on.
I do believe it would be beneficial in the case of when a selection is made as well if a new user was trying to time shift just the selection then would see that all the clips that the selection includes are selected.
I hope I am articulating that well enough . . .