WordPress, other CMS & shop systems
I have set up WordPress instances myself from scratch and have a good overview of the WP ecosystem.
Apart from WordPress, I have worked with numerous CMS to manage website content, ranging from complex corporate solutions like Adobe EM to straightforward ones like Drupal. I have provided trainings and support for these and written documents/recorded videos showing how to use them.
I have even worked on a CMS myself, as a part of Styla team developing their own tool. I learned to evaluate users' feature requests against the most important use cases to decide whether they make sense to most other people using the tool. I could do this for any CMS.
Apart from pure content systems, I have experience with shop systems like Magento, BigCommerce, Shopify, SalesForce, Hybris, and understand how inventory and orders are managed and bound into workflows. I have worked on writing plugins for such systems too.