The Airtable trigger list is empty because Make is not seeing any valid trigger field coming from that table yet.
Make only populates that dropdown when Airtable has at least 1 field of a supported type (for example a Created time or Last modified time field), so there is nothing to show right now.
Here’s what you can do:
Add or configure a proper trigger field in Airtable first, save the table, then reopen the Airtable module in Make and refresh the fields.
Note: Once Airtable exposes a valid trigger field, it will appear in the list.
Let me know how it goes!