Extending Structure Field


in Kirby 2 we extended the structure field (by first copying the folder from /panel to /site/fields and then modifying the files) to add the DataTable-Library (JS) to it (showing/hiding columns, sorting columns, pagination, search etc.).

How can we achieve in Kirby 3 to get a similar customization? The docs on custom fields are not really clear on that to me.

This might help if you try to do something similar: https://getkirby.com/docs/cookbook/extensions/first-panel-field