FeedMe Pro Import JSON When I import using JSON with FeedMe Pro and need to import more records into an entry that has a Matrix field. I find it deletes the previous and adds the new data only.  Is there anyway to append to the Matrix field leaving the previous data intact?
In addition to How to save Matrix data programmatically in Craft 3 

You'll fetch your data loop each row and fetch the element / create a new element if none exists

$section = Craft::$app-&gt;sections-&gt;getSectionByHandle('news');
$entryTypes = $section-&gt;getEntryTypes();
$entryType = reset($entryTypes);
foreach ($jsonData as $row) {
    // try to fetch an element
    $element = Craft::$app-&gt;getElements()-&gt;getElementById($row['id']);
    // no element exists, create a new one
    if ($element === null) {
        $element = new Entry(
            [
                'sectionId'     =&gt; $section-&gt;id,
                'typeId'        =&gt; $entryType-&gt;id,
                'fieldLayoutId' =&gt; $entryType-&gt;fieldLayoutId,
                'authorId'      =&gt; 1,
                'title'         =&gt; 'My Entry',
                'slug'          =&gt; 'my-entry',
                'postDate'      =&gt; new DateTime(),
            ]
        );
    }
    // get the field by handle
    /** @var \craft\fields\Matrix $field */
    $field = Craft::$app-&gt;getFields()-&gt;getFieldByHandle('matrix');

    // get the existing matrix blocks
    $existingMatrix = $element-&gt;getFieldValue('matrix');

    // serialize the data
    $serializedMatrix = $field-&gt;serializeValue($existingMatrix, $element);

   // loop your json matrix blocks
    foreach ($row['yourMatrixBlocks'] as $key =&gt; $block) {
        // append your new Matrix fields
        $serializedMatrix['new' . $key] = [
            'type'   =&gt; 'block',
            'fields' =&gt; [
                'field' =&gt; $block['field']
            ],
        ];
    }

    // set the new field value
    $element-&gt;setFieldValue('matrix', $serializedMatrix);
    $success = Craft::$app-&gt;getElements()-&gt;saveElement($element);

    // display errors - just in Case
    if($success === false){
        Craft::dd($element-&gt;getErrors());    
    }
}