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Create your Confluence space homes. E.g., Refined for Confluence Documentation Space Home.
Use the Site Builder to create categories and subcategories in your site (+ symbol).
Organize (drag and drop) your spaces into the respective subcategories and categories.
Disable the dashboard home on the subcategory if you wish. You can also decide to disable the category home. We disabled ours on our product category home as well as subcategory homes. Click Category settings cog → Check “Disable Category Home”.
Add a custom URL to a category 3 to convert it into an external link.
Now your site navigation should look like this:
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3. Customization
4. Personalization
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