Using remainder of OPT extension in second Masters

I completed my Masters in 2016 and started my job on OPT. I then got my OPT Extension for 2 years. I used only 6 months of the 2 years extension when my H1B was approved that left me with 1 and 1/2 years of unused OPT extension. I might be doing a second masters in the future to further enhance my skill set and also improve my chances of a Phd in my field of interest but would like to have some experience before the Phd admission. I was wondering if i could use my remaining extension period for a OPT after the second masters to get employment??

Well, there is no official documentation anywhere that tells that you can split your STEM OPT duration between degrees. You need to check and validate with the DSO at the new school to make sure you can do it.