Besides Annasaheb Dabholkar's work, did anyone else write biographies of Sai Baba?

Yes, the source material from Chapter 0 confirms that other biographies of Sai Baba exist. Notably, Shri Dasganu Maharaj, described as a foremost modern poet who was worthy of Baba's grace, wrote two biographies. The first is located in his work Bhaktalilamrut (Chapters 31, 32, 33), and the second can be found in Bhaktisaramrut (Chapters 52, 53). These biographies are praised as excellent and heart-touching but are noted as being very short, especially in comparison to the Shri Sai Satcharita.