In the transition effect dialog for an image track, I can select "Apply to all objects in the track".

However, the same option is not available for subtitles on a different track.

Of course, I'd like to have the same transition effect for both images and subtitles, that is, to have them in sync.

I've found one workaround: I move the text objects to the end of the image track, and then select "Apply to all objects in the track", which results in identical transitions for both images and subtitles. After that, I move the text objects back to their own track.

Still, one would think that there is a better way of accomplishing this.