Both are JS code, which would make the solution fragile? Because it depends on the implementation of VirtualList. I hoped for a Java only solution. After all, that is what Flow is about, right? It makes no sense to me to provide a VirtualList component with a scrollToIndex method, but no way to listen for or get the current displayed index. It’s like a half baked cake. 
Anyhow, if this is the only way, then that is the only way. Thanks!