While adding the default route for route domains, Route domain options not showing

Use route domain postfix on the destination and the gateway entries e.g.

Destination: 0.0.0.0%67
Netmask: 0.0.0.0
Gateway: 10.10.10.10%67

On TMSH your route should look like this

net route default_route_67 {
    gw 10.10.10.10%67
    network default%67
}