It's impossible to move a placeable, but you can create the illusion of movement.
Create a new placeable a short distance from the original, then delete the original. Using DelayCommand and ExecuteScript, run the same script on the new placeable after a short delay. Continue until the end position is achieved (you don't want a script to run forever!).
The results are a bit jerky and resource-hungry, but you can fine-tune the distance and timing to make it look better.
The other way to create the illusion of motion, which is really smooth and efficient, is an animation. Oseryn's
Sailing Ships is an excellent example; the ship can appear to sail from horizon to horizon if you like, though technically its location never changes. However, making animations requires expertise that few of us have mastered.