Initial

Plugin/Order/View/ItemsColumns.php

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+<?php
+namespace Shopkeeper\OrderItemsCustom\Plugin\Order\View;
+
+class ItemsColumns
+{
+    /**
+     * Modify the columns array to remove tax columns and add cost column
+     *
+     * @param \Magento\Sales\Block\Adminhtml\Order\View\Items $subject
+     * @param array $result
+     * @return array
+     */
+    public function afterGetColumns($subject, $result)
+    {
+        // Remove tax columns
+        unset($result['tax-amount']);
+        unset($result['tax-percent']);
+
+        // Add cost column after price
+        $newColumns = [];
+        foreach ($result as $key => $value) {
+            $newColumns[$key] = $value;
+            if ($key === 'price') {
+                $newColumns['cost'] = 'Cost';
+            }
+        }
+
+        return $newColumns;
+    }
+}