Do you want them to be able to edit existing entries as well? do you plan to run this locally only, or does it need to be scalable and deployed to server?
Take a look at this interactive view based component. It is a bit more complex than is needed because of all of the dropdown requirements, but the general use of the table editor node with a drop-down to log an entry or adjust an entry may work for your use case.
Basically, you could add a blank row to the bottom of the table every time and have it available for editing via direct entry, and have all of the existing entries available for edit in the same place.