How do I display an alternate theme? The preview_theme_id parameter no longer works.
It seems like if I click preview theme from the admin, a cookie or token is set because it becomes the default when I check the front end logged in.
Also, I notice that in customize theme homepage editor, the iframe Shopify uses has an empty preview_theme_id parameter. If I open the iframe in a new tab, the theme switches to the default theme. Exact same URL - different theme.
Not sure why Shopify is making the theme preview so cryptic... why remove the preview_theme_id functionality?