Add Webhook Column to Existing Clay Table

Yes, you can add a webhook column to an existing table and position it as the first column. First, set up the webhook by going to your Clay home page, clicking + Create New, selecting "Import data from Webhook" in the "Other" section, then choose your existing table. To make it the first column, right-click on the current first column and select Insert Left to add the webhook column before it.

Sources: Insert Column Left, Right Import Data to Clay Using Webhooks