Category levels

I am viewing the “Examples” using GD core” In the example for instance it shows:

Category (restaurant) Sub-category (French) Listing (L’escargot)

Here is what I need:

Category (Contractor) Sub-Category (Plumber) Sub-sub category (boilers, fire sprinklers, plumbing, sheet metal, pipes and vents for gas.

I believe I read somewhere that we cannot do sub-sub-categories two levels deep. How would you suggest I handle this with “tags” for the sub-categories.

If I can only use tags for the “Category” level there will be hundreds as it applies to Contractor’s across the spectrum of various Contractors.

Where as there are only certain sub-sub categories that would pertain to say and “Roofing Contractor” that does not need a tag for plumbing.

Guidance and suggestions please?
Kind regards

I am working on a “master” primary classification spread sheet and a sub-category spread sheet to import. (translating it to gd syntax that would be Sub-category and sub-sub-category)

Ok, now looking at this further, please confirm this, I can Create the gd sub-category and then make the sub-sub-categories “Children”? Or, in other words the Sub-category will be the parent (sub-category)

Thus I will have Contractor, Plumber (parent), gas lines (child) correct? If yes, then how do I go about importing the “children” and putting with their Parent? Sounds like a family thing… lol.