How to override a node in an xml file of a ui_component

I have this xml file in some third party module having this content

<?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="actions">
        <field name="simple_action">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="sortOrder" xsi:type="number">10</item>
                    <item name="template" xsi:type="string">Mexbs_ApBase/form/element/simple-action</item>
                </item>
            </argument>
        </field>
        <container name="action_details">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="sortOrder" xsi:type="number">20</item>
                </item>
            </argument>
            <htmlContent name="html_content">
                <argument name="block" xsi:type="object">MexbsApBaseBlockAdminhtmlPromoQuoteActionDetailsStaging</argument>
            </htmlContent>
        </container>
    ...
    ...
    </fieldset>
</form>

and then I want to change this block URL inside the below htmlContent node

    <htmlContent name="html_content">
                <argument name="block" xsi:type="object">MexbsApBaseBlockAdminhtmlPromoQuoteActionDetailsStaging</argument>
   </htmlContent>

to “MexbsApBaseBlockAdminhtmlPromoQuoteActionDetails”

I have already created a module to override the file, and tried to do so by rewritting the whole file in my own module with the intended changes made and it worked, but I want to only include this node needed to be changed in my file not the whole file.

How can I do so?
Thanks in advance