Connect different islands

I have 3 islands, A B C. I’m using layered graphs. The islands are consecutive, connected.
What I’d like to do is move island A instead of B, so I have A connected directly to C ( B is gone ).
Should I :
1 ) Rescan everything, or
2) Save a graph for A B and C, and load it ? and if so, how can I connect A and C in this case ?
is there any other alternative way or a better suggestion ?