I think you missed what I was meaning. While it's true you cant have full control over the movement by using transitions alone, you can use combinations of different transitions that quickly and easily give alot of creative control in the movement of the PiP. Again, it's the "moving" transitions that I'm talking about: slide, swap, zoom, spiral etc. as opposed to the "revealing" transitions.
If you've set up a static PiP on an overlay clip, and then use a moving transition on the overlay clip, the movement is imparted to the PiP automatically. You dont have to set up beginning and ending keyframes for the PiP. In addition, it solves the problem of locking the PiP window onto the section of the video you want to show without having to marry the pan/crop settings with the movement rate.
For example: You can set up a PiP on the overlay. Then add a spiral transition to the start of the overlay clip. The locked PiP will spiral in over the main video. You could then let the PiP dwell in place for a second or two. Then use a slide down (or any angle for that matter) to slide the PiP off screen. It's very quick and easy, doesnt require that you do anything to your main video clip and is easier than setting an animation on the PiP itself.
You could also combine these transitions with PiP keyframing so that you could get 4 movement changes during one PiP clip.
Some other simple examples: Use a swap transition on the overlay PiP to make the PiP appear to come out of a slit in the middle of the main video moving first to the right and then sliding left over to it's resting position in front of the main video. Literally all you have to do is add the transition to the overlay clip that you've already established as a PiP.
You can use a slide in from left transition and a slide out to right transition on an overlay PiP. If you drag each transition so they meet in the middle of the clip then the PiP will effortlessly come from off screen and move all the way off screen again without doing anything but adding the two transitions.
You can come up with an endless variety, and all as fast as dragging and dropping any transition that "moves" the video rather than just revealing the video (like a wipe for instance).
My point was that this is an easy way to give movement to the PiP and can usually handle most movement tasks using a transition preset, without having to set the beginning and ending keyframes manually or experimenting with matched timing in order to maintain a lock on the inset video.

One other PiP control that can be useful is the "Repeat X" and "Repeat Y" commands. As long as you dont need to move multiple PiP's in independent directions, you could use the repeat parameter to build multiple PiP windows on one overlay (like with the PiP text menu that was discussed before). This would eliminate having to render multiple passes to build multiple PiP's that all move the same. Doesnt solve the independent movement problem of course, but oh well...
Now if we could only adjust the aspect ratio of the rectangle! Has anybody figured out a work around for that?

Ok, one other way to state it... What I'm doing is using transitions such as slide, swap, spiral, push, zoom, etc to impart movement to the overlay PiP. This movement doesnt make the PiP move across the overlay video, the overlay window is locked with the section of the video you originally set up with the PiP menu. The locked PiP moves across the main video without having to marry the Pan/Crop settings to any specific movement rate. There's no need to set any beginning or ending keyframes, you just need to set the Pan/Crop to your satisfaction once and then let the transition take care of moving the PiP.
I'm not talking about using transitions to change from one image to another image, i'm using transitions to quickly and easily impart locked PiP movement automatically.
This works because the specific transitions i've mentioned move the entire overlay frame from off-screen to on-screen automatically. But only the PiP window is visible as this occurs.

SoundGuy63

Brilliant analysis! Very very useful - definate "keeper"!

Best regards

Grazie