Advanced Sessions Plugin

Hi @! Is there feature that can be used with seamless travel while join session?
I used Online Subsystem Null. JoinSession blocks the engine while loading. But I need to load transition level at loading time.
I tried to override ClientTravelInternal_Implementation and substitute seamless travel args to inherited call, but after joining it get back to main map.
It will be nice to use function like AdvancedJoinSession(bSeamless=true)

Thanks!