A plugin inventory makes updates and handovers easier. It gives the site owner a record of why each plugin exists and which features rely on it.
For every plugin, record its purpose, whether it is active and where its settings are managed. If it handles a contact form, note which page contains the form and who receives messages. If it modifies design, name the pages that use it.
Before removing or replacing a plugin, check the inventory for dependencies and confirm that the replacement supports them. After an update, test the affected pages and record the result. Review the list whenever you add something new.