Communication custom fields and categories are created via the control panel settings (permissions required to access control panel).
Go to Control Panel > Communication custom fields > Add category
Similar to Contact custom fields, the Communication custom fields are recorded underneath categories. The "Uncategorised" category is a system default category available to use if needed. Categories display as tab headers in the Add Communication window.
Click the "Add" button in the top right corner of the screen to add a category. Define the category name according to the business requirement.
Use the same "Add" button to select a custom field type to add within a category. A combination of similar or different custom field types can be used within each category type. Choose one of the Text, Number, Select, Date and/or Time, Lookup or Multi-Select field options from the "Add" drop-down. Then use the Category drop-down to assign that custom field to its respective category. By default, all custom fields are assigned to "Uncategorised” if one is not assigned.
Use the option to drag and drop custom fields and categories to arrange their placement. The Add Communication window will display categories and fields in the same order as laid out in the control panel settings.