Having a similar user story, we implemented a Generic Javascript View node (JS code) which reads the content of the table, creates an HTML table from that, and adds one dropdown per row into the last column of this custom table visual. I cannot share our code but it is quite straightforward.
Output vairable can be a dictionary between your original rowID and the newly input values, so you could join the manually selected values back to your original table.
However, when it comes to 200k lines, this approach might get too slowly performing (our case works well but we have only ~100 lines max)
I hope this helpful to you, bests,
Csaba