Recertification -- NSE7

You can check this link:
Exam Policy - Recertification : Help Desk

It gives a full overview of how renewal works. You should first check your profile on how your NSE7 is converted to FCSS or FCP and from there consult with the above link.

You can read here, https://training.fortinet.com/local/staticpage/view.php?page=fcss_network_security in the right panel where it says Recertification, this is for Network Security specialization. So, if i understand this correctly a new specialization cert would not extend a existing one from a different path.

Basically, you would need to either pass FCX exam or go again through the exams required for the certification in question, e.g. OT Security requires the core exam to be taken again for re-certification/extend, Sec Ops one elective and so on.