Creating a custom Magento 2 indexer requires development knowledge. Here is a step-by-step technical overview:

1. Define the Indexer in indexer.xml - Declare your indexer with a unique ID, class, and view ID inside etc/indexer.xml of your module.
2. Create the Indexer Class - Build a PHP class that implements \Magento\Framework\Indexer\ActionInterface with executeFull(), executeList(), and executeRow() methods.
3. Define the Mview Configuration - Create etc/mview.xml to subscribe to database table changes and trigger partial reindexing automatically.
4. Register the Module - Ensure your module is properly registered via module.xml and registration.php.
5. Run Reindex - Once deployed, trigger the custom indexer via CLI or directly through the Magento 2 Backend Reindex from Admin Panel Extension for a no-code reindex experience.

For most store owners, managing and triggering existing indexes efficiently is the priority — which is exactly what the Magento 2 Admin Panel Reindex Extension is built for.