Click a button of the page's action bar (.page-main-actions: "Add New Page", "Hold", "Delete", "Flush Cache Storage") or of the bar above the category tree ("Add Subcategory") and wait for what follows.
Examples
When I click the "Add New Page" page action
When I click the "Hold" page action
And I click the "Add Subcategory" page action
When we click the "Flush Cache Storage" page action
When I click the "Back" page action
Pattern
When(/^(I |we )*click the "([^"]*)" page action$/, …)
Part of @webship-js/magento-steps (github.com/webship/magento-steps), a step pack for Webship-js 2.0.x.