Octane nodes can be placed into Modo sub-assemblies with exposed inputs and outputs. If you are creating the inputs/outputs manually, the only requirement is that the Modo User Channel Type must be set to Float.
These sub-assemblies can be saved as reusable presets, via Right Click > Save Assembly Preset...
The following video shows some working examples:
https://www.youtube.com/watch?v=jbjOkOr2174