In the multiselect tutorial, in the part that shows how to use a JSON file via the API, we have a list of companies and their products.
We see how to call the names of the companies.
It might make sense to use two different routes and return the data you need for the subcategories from that second route, i.e. a flat list of all products in the example.
Not related to your
One problem I see with your category/subcategory approach is that users could select Apple as category and then Windows as subcategory, if the subcategory list is not filtered.
For filtering by category/subcategory, I saw that the best solution was to make a custom selection field. It’s in the works, but, not being very comfortable with Vue at the moment, I’m trying to find an intermediate solution.
So, with your answer, I could do what I had in mind!