This plugin is no longer maintained.

You will find the updated source code on his development repository at https://github.com/inpsyde/google-tag-manager.

I cannot save data entered in the settings screens. When I click save, the data entered is removed – all is blank again. Also no code output. It looks like a jQuery/JavaScript issue/conflict.

In the admin view you can set the user role for visitors but when I leave the field empty it still uses "visitor" as value for user.role. I think the best value would be undefined (not a string!) or just don’t push this variable. It would help to set things up in GTM, where the undefined value can be used e.g. to send no value to Analytics.