With the changes in the modification workflow introduced in the Happy Valley release, you can no longer define template defaults for a variation without a template. Template defaults are now only valid for variations that actually use a template for their content. If your site has modifications that use template defaults (template data or content) without an actual template, you can no longer edit and save the variation content. You may end up with a variation like this if you, for example, try to activate or duplicate an old, inactive modification.
To be able to edit the variation content, you must first create a template for the variation, using the original variation content as a basis, and then select that template for the variation.
To create the template and select it for the variation:
Select the template you just created and click Select. You can now edit the existing template defaults.
When you're done, click Save.
For more information about defining and editing modification content, see Defining the content for a modification.
For more information about working with templates, see Templates.