I am on a B2 visa and entered the USA on July 15th 2019. My I94 was supposed to expire on January 15th 2020. But I had applied for extension (I-539) on November 4th, 2019. On March 30th 2019, I received a RFE notice and USCIS has given extra 60 days to submit those evidences because of this pandemic. I was wondering, if I can apply for the extension (I-539) again after USCIS makes the decision on my first extension.
Yes, you can apply for an Extension of Status again after your first Extension of Status is approved. There is no limit to the number of times you can apply for Extensions of Status in a row, though the chances of approval decrease with each additional time.
In fact, you can apply for an Extension of Status again even if your first Extension of Status is still pending, but it will only be considered if your first Extension of Status is approved, and the period of the status that is granted by the first includes the day you filed for your second Extension of Status.