Are there any exercises to move a low-lying placenta?

No. In fact, it is best for a woman with a low-lying placenta to seek input from OB provider early about what to do and, above all, what not to do!
No. You can not control the location of your placenta. In fact, the placenta does not move at all. The placenta is attached to the uterus and is locked into place. The uterus grows throughout the pregnancy. As it grows it will carry the placenta away from the opening of the cervix. Docs often talk about the placenta "moving" as a way of illustrating this complication of pregnancy.