Where should I place the tag code for Google Tag Manager?
Google Tag Manager Code that needs to be placed on every page in the store should be placed in the Layout Section / Edit Advanced Layout / Head Addendum field.
In Tags, variables are used to capture dynamic values. To capture dynamic values (e.g.: passing the transaction value and products purchased to a conversion tracking tag) additional tag code must be entered into the Settings Section / Edit Policies Addenda and Disclaimers / Order / Affiliate Addendum. For Addendum Position choose, 'Body Paragraph'