$categorySetup->addAttribute(Category::ENTITY, 'roflcopter', [
                    'type' => 'int',
                    'label' => 'CMS Block',
                    'input' => 'select',
                    'source' => 'MagentoCatalogModelCategoryAttributeSourcePage',
                    'required' => false,
                    'sort_order' => 20,
                    'global' => MagentoEavModelEntityAttributeScopedAttributeInterface::SCOPE_STORE,
                    'group' => 'Display Settings',
            ]);

<?xml version="1.0" encoding="UTF-8"?>
<form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
    <fieldset name="Navigation">
        <argument name="data" xsi:type="array">
            <item name="config" xsi:type="array">
                <item name="label" xsi:type="string" translate="true">Navigation</item>
                <item name="collapsible" xsi:type="boolean">true</item>
                <item name="sortOrder" xsi:type="number">100</item>
            </item>
        </argument>
        <field name="roflcopter">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="sortOrder" xsi:type="number">60</item>
                    <item name="dataType" xsi:type="string">string</item>
                    <item name="formElement" xsi:type="string">select</item>
                    <item name="label" xsi:type="string" translate="true">Roflcopter</item>
                </item>
            </argument>
        </field>
    </fieldset>
</form>