This is the = command that adds a new column based on a Python expression you provide. You can reference the cells in the current row based on the column name.
It is also possible to create a column based on the output of a shell command.
VisiData is row based, not cell based, so you cannot create expressions that reference data across rows.
Much as I love org-mode tables, I'd say the only axis where an org table is more feature rich is the formula support. Visidata is an amazing multitool for exploring tabular data that supports many data sources. From an ergonomic perspective, visidata wins.
2021 (69 points, 6 comments) https://news.ycombinator.com/item?id=28078980
2020 (203 points, 22 comments) https://news.ycombinator.com/item?id=24774947
2018 (195 points, 40 comments) https://news.ycombinator.com/item?id=16515299