The ways to install the "Nested numbered lists for the block editor" plugin are described here.

In your WordPress backend Go to Plugins > Add plugin. Search there for "Play Audio Once". Click on "Install" for the plugin and then on "Activate. Install manually Go to the official plugin website and click on "Download". In your WordPress backend, go to Plugins > Add plugin and click on the "Add plugin" button. In the file dialog, select the file you downloaded in step 1 and upload it. Then activate the plugin. Install via FTP Go to the official plugin website and click on "Download". Then upload the ZIP file via FTP to the directory "/wp-content/plugins/". Activate the plugin via the „Plugins“ menu in WordPress.

Play Audio Once - WordPress Plugins by Thomas Zwirner

WordPress plugin

free of charge

Plugin page:

https://de.wordpress.org/plugins/play-audio-once/

Support forum: https://wordpress.org/support/plugin/play-audio-once/

GitHub repository: https://github.com/threadi/play-audio-once

Play audio once

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Installation of „Play Audio Once“