If you want to add a new custom attribute in product tabs, then you you need to add the below code:

<referenceBlock name="product.info.details"> 
 <block class="MagentoCatalogBlockProductView" name="product.info.keyfeature" as="keyfeature" template="Magento_Catalog::product/view/attribute.phtml" group="detailed_info">
 <arguments>
 <argument name="at_call" xsi:type="string">getKeyFeatures</argument>
 <argument name="at_code" xsi:type="string">key_features</argument>
 <argument name="css_class" xsi:type="string">keyfeature</argument>
 <argument name="title" translate="true" xsi:type="string">Key Features</argument>
 <argument name="sort_order" xsi:type="string">20</argument>
 </arguments>
 </block>
 </referenceBlock>

in your theme/Magento_Catalog/layout/catalog_product_view.xml file between the body tag.

Here I have set “key_features” product attribute in product tabs.