Just to expand a bit more on this:
The applicationId is used to keep track of the original object in the software it was in when it was converted ToSpeckle.
This makes sense in programs like Revit, Rhino, etc… where anything you create exists in the model. But not so much in GH where everytime you press F5, the entire thing is re-generated (and hence, will have new guid values (where available).
So adding the applicationId to conversions in grasshopper would be quite ineffective, as you’d never be able to map anything back to that specific object in GH once the solution was recomputed.
Maybe we’re not understanding fully your use-case though, could you share more details of what you intend to use the applicationId for?
I can see some exception where this could be directly applicable though: Objects referenced from a Rhino doc (i.e. if it’s not a GH geometry, but a referenced geometry from Rhino it should have a consistent guid you could track) Not sure what @teocomi and @dimitrie would think about this.
Edit:
I created an issue for that particular edge-case we’re not covering (but should) GH: ApplicationId's for objects referenced from Rhino · Issue #1103 · specklesystems/speckle-sharp · GitHub
Also, manually creating your own applicationId and assigning it would also work like a charm.