If you are just looking for failover normal floating static route.
then the below config must work.
configure iproute add 192.168.37.0 255.255.255.0 192.168.92.1
configure iproute add 192.168.50.0 255.255.255.0 192.168.92.1
configure iproute add 192.168.50.0 255.255.255.0 192.168.200.1 200
configure iproute add 192.168.37.0 255.255.255.0 192.168.200.1 200
configure iproute add default 192.168.92.1
When one of the nexthop fails do you see that route removed from Fib?