There are many practical applications for static routes. Static routing is often used at the network edge to support attachment to stub networks, which, given their single point of entry and egress, are well suited to the simplicity of a static route. In Junos OS, static routes have a global preference of 5. Static routes are activated when the specified next hop is reachable.
You can specify options that define additional information about static IPv6 routes. These attributes, for example a community tag or route metric, are included with the route when it’s installed in the routing table. These additional route attributes are not required for basic IPv6 static routing.
To set a default route you'll need to configure it at the "routing-options" hierarchy level and specify the routing table: [edit routing-options] user@R1# set rib inet6.0 static route 2001:db8:2::/48 next-hop 2001:db8:1:1::2
https://www.juniper.net/documentation/us/en/software/junos/static-routing/topics/topic-map/config_static-routes.html#id-example-configuring-ipv6-static-routes