What's the best way to import 1M rows into a table? Ideally I can use the dashboard somehow

AFAIK, csv import is available only on table creation? However, getting a 1M row csv file uploaded is not easy. Or is it? Are there better ways?

I've managed to upload 100K rows so far. Would there be a way to append multiple tables into one large table (or view)? All the tables have the same header row.

Thanks so much in advance!