Plots generated via the display() command are automatically saved under /FileStore/plots. See the documentation for more info: https://docs.databricks.com/data/filestore.html#filestore.
However, perhaps an easier approach to save/revisit plots is to use the pandas api on Spark built-in plotting (part of Spark 3.2/DBR 9) if you're comfortable writing Python code. You can also log them as MLflow artifacts.