I've set up parameter modulation to facilitate video-in-video. I automated the zoom parameter of the video plugin and linked it to the x and y offset parameters so that when I automate zooming (out) of the video, it will not only decrease in size but will also drift to the left of the screen to make place for the other video. This is much more convenient than to manually automate x/y offset.
I used another instance of the same zooming plugin and inverted the parameter modulation of the x parameter to make the video shrink to the other (right) edge of the screen.
The parameter modulations work, however, when I render the project, x and y parameter modulations are ignored. They also seem to get ignored from time to time while working on the project.