You can write to any kind of datasets using the Dataiku API: https://doc.dataiku.com/dss/latest/api/python/datasets.html. This API contains several methods for writing to datasets.
So the example code you posted is the right way 🙂
Just a comment on the approach: if you use a dataset as a "backend" element of a webapp, this dataset will be shared among all the web app users. So it could lead to edit conflicts if you have multiple concurrent users. Would that be the case for you?