There is no autofill command. What this user did was create a list on the side (out of view, probably in a text editor) that he used to fill that {1-to-Many} field. That list probably looked like this:
1
2, 1
3, 2, 1
4, 3, 2, 1
...etc
Copying and pasting that into a link field would create links to records matching those names between the commas. Unfortunately there isn’t a way to do this natively in Airtable, outside of writing a script in a Scripting app to create the links.
