Show dev mode and Yii toolbar on secondary site I am unclear on how to turn on dev mode as well as the Yii toolbar when viewing a secondary site in Craft.
devMode is a general config setting and it applies to the whole Craft installation (regardless of the site if you're running a multi-site Craft installation.

The Craft debug toolbar is a user account preference to enable and it should work across all sites in a multi-site installation as well.