Best practice to combine sub-category selection and drilldown in Mobile navigation

I'm working on a mobile application that allows selection of a category on one of its screens. For example:

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There can be more than 2 levels in the hierarchy and the amount of items is not limited by the app. Users can customise the categories to their liking.

On each of the screens the user should be able to:

  • select a category/subcategory, OR
  • drill down into the subcategory (see the second screenshot)

How would you implement such a UI? Do you know any good examples where this issue has been solved? I would really appreciate your help.

It's been puzzling my mind over the last couple of weeks. I've came up with a couple of solutions but they all just feel wrong, not something that would fit the mobile UI/UX.

Thanks!

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