https://docs.magento.com/m2/ce/user_guide/catalog/category-hidden.html

There are many ways to use hidden categories. You might want to create additional category levels for your own internal purposes, but show only the higher-level categories to your customers. Or, you might want to link to a category that is not included in the navigation menu.

To create hidden categories:

1.

On the Admin sidebar, tap Products. Then under Inventory, choose Categories.

2.

In the category tree, select the category you want to hide. Then, do the following:

a.

Set Is Active to “Yes.”

b.

Set Include in Menu to “No.”

3.

In the Display Settings section, set Anchor to “No.”

The hidden category is active, but does not appear in the top menu, or in layered navigation.

4.

Although the category is hidden, you can still create subcategories beneath it, and make them active. Complete the following settings for each hidden subcategory:

a.

Set Enable Category to “Yes.”

b.

In the Display Settings section, set Anchor to “Yes.”

As active categories, you can now link to them from other places in your store, but they will not appear in the menu.

5.

When complete, tap  Save .