Noam, Thanks for your reply.
I understand that FPGA resources of Pluto are very less but still I want to add some custom counter/ state-machine in the Pluto FPGA. I think they will fit in the available resources. I have studied the Mathworks documentation about registering the Custom Board but I am unable to find the required files e.g xps project on Analog Devices website. Can you plz guide me in this?