Nested Select in panel

The CMS Questions
2

The first thing that comes to mind is the field toggle field, but it is a radio field, not a select and it would require different fields, not one. So not really ideal.

Another option would be a single select, that contains the options like this:

options:
 option1: Health: Fitness & Nutrition
 option2: Health: Whatever

You’d need some category mapping:

c::set('options', [
'option1' => [
  'category' => 'Health',
  'subcategory' => 'Fitness'
 ]
]);

And the idea you already had yourself with the two selects, but that would require some coding on your part.