Hi, I understand it's a bit frustrating not being able to (re)set password directly from the community portal via My Profile or My Settings. But those are global accounts handled by FortiCare system, now.
IAM accounts Administrators can reset users' password and so trigger the change for them.
IAM Users can (if not prohibited by admin setting, as in my case) change their password directly.
Just login for example to https://support.fortinet.com and on top right corner you'll have this menu..
Security Credentials will bring you to your password change.. (unless your account is fully managed as in my case so I can't show more)
Tom xSilver, planet Earth, over and out!