Instead of creating a new topic, you can bump a topic by adding a post to it, maybe @mentioning people that you think could help.
These VTK’s interactors are good for simple examples and can serve as a basis for implementing interactors in full-featured applications.
If there are simple changes that you would recommend that would make your life easier then feel free to send a merge request.
If you want to have a 4-pane viewer then I would recommend not to reimplement this from scratch, as it will become very complex very quickly as you are adding features. Instead, find a VTK-based application that already has this feature (ParaView for engineering visualization, 3D Slicer for medical visualization, etc.) and extend/customize these application frameworks to do exactly what you need.