It works the same like on ROSv6 (for which you have tens of topics here) except that the syntax of the configuration has changed a bit - the routing tables now have to be explicitly created first (
/routing/table/add name=xyz fib) and the parameter of a route that indicates a routing table name is now
routing-table instead of previous
routing-mark (whereas it is still
routing-mark in mangle rules).
As for functional differences, recursive next-hop search now works even if the
gateway is not an IP address, which is great especially for PPPoE (see
this if you don't know what I'm talking about).
And in the latest ROS 7 versions, the mutual priority between routing marks assigned in mangle and routing table names assigned by routing rules has changed, so if you were used to override the mangle verdict with a routing rule verdict, you have to change the approach. Which is not so great if your ability to access a device remotely depends on the old behaviour, but it should not be your concern I guess.