Were there any seemingly miraculous elements associated with how Sai Baba slept on the suspended plank?

Yes, Chapter 0 highlights several miraculous aspects of this event. Firstly, the plank was suspended by old rags that appeared too weak to even bear the weight of the plank itself, yet they securely held both the plank and Maharaj's body. This was attributed to Maharaj's divine power. Secondly, despite many people keeping watch in an attempt to see him, no one ever witnessed Maharaj climbing onto or getting down from the suspended plank. His method of ascent and descent remained a complete mystery to all observers.