If you'd like to organize your custom attributes in categories under the custom tab you can do so by going to Settings > General > Custom Attributes. For example, if you want to group your custom attributes that are imports as "Imports," this is where you can categorize them.
You can edit any existing custom attribute by clicking on the triple-dot menu to the right of the attribute and select "Edit."
You then can start typing the custom attribute category name that you would like to update or choose an existing category.
When you're finished updating your custom attribute click the "Update" button to save. These till not be editable after creation so be sure you double check your Category name.
You can also add in a custom attribute category right from creating a new custom attribute by clicking "New Custom Attribute."
Once you added an attribute category, you can see which category the attribute belongs to by going to Settings > Custom Attribute.
Your attribute will then be added to a custom attribute category which is located under the "Custom" tab in a profile.
Attributes that are not categorized will be grouped under "Uncategorized" in the Custom tab of a profile.