No, based on my first suggestion where you add additional columns, it would be something like this.
| Category | SubCategory-Category | SubCategory | ThirdCategory-SubCategory | ThirdCategory |
|---|---|---|---|---|
| Arts & Collectibles | Arts & Collectibles | … | … | … |
| Automotive | Automotive | Car & Truck Parts | … | … |
| Baby | Automotive | Motorcycle Parts | … | … |
| Books | Automotive | Wheels & Tires | … | … |
| … | Baby | … | … | … |
| … | Baby | … | … | … |
| … | Baby | … | … | … |
| … | Books | … | … | … |
| … | Books | … | … | … |
| … | Books | … | … | … |
But in honestly, based on my second suggestion, I think this would be better since you wouldn’t have to add extra columns and you can use the ones you already have.
| Category | SubCategory | ThirdCategory |
|---|---|---|
| Arts & Collectibles | … | … |
| Arts & Collectibles | … | … |
| Arts & Collectibles | … | … |
| … | … | … |
| Automotive | Car & Truck Parts | Carburator |
| Automotive | Car & Truck Parts | Engine |
| Automotive | Car & Truck Parts | Steering Wheel |
| Automotive | Motorcycle Parts | Clutch |
| Automotive | Motorcycle Parts | Forks |
| Automotive | Motorcycle Parts | Brakes |
| Automotive | Wheels & Tires | All-Season |
| Automotive | Wheels & Tires | Off-Road |
| Automotive | Wheels & Tires | Touring |
| … | … | … |
| Baby | … | … |
| Baby | … | … |
| Baby | … | … |
| … | … | … |
| Books | … | … |
| Books | … | … |
| Books | … | … |
| … | … | … |