Previously, we could go to Online Store -> Preferences, and enter the Facebook Pixel ID into a text input. This was all we had to do - this made Shopify send tracking data to the Facebook Pixel.
Today, it appears the only way to set the pixel is to first connect the store using the Facebook app. That seems unnecessary: we should at least have the option to simply enter the pixel ID by hand as before.
I'm sure this was done with the intent of streamlining setup of Facebook Ads, but it puts some of us partners (who build the store but don't manage Facebook) in a difficult position. For us, it means we can no longer ensure continuity of Facebook Pixel data for our customers moving off of Magento who already had tracking configured the way they wanted it.
And it's not a stretch to see how this could affect many partners. Envision this not-so-hypothetical scenario:
Facebook Pixel tracking already in place. But the pixel itself, and the ads relying on it, are all managed by 3rd party marketing companies in many cases.
So while we may know the pixel ID, we don't have the ability to tell Shopify to use it, because we'd need to be an admin of the business manager account.
For a small mom-and-pop merchant, that might not be a problem. But when working with a large org, even figuring out who has this level of access can be a nightmare.
This other forum thread mentions the change, but doesn't call out the impact: https://community.shopify.com/c/Shopify-Discussion/How-to-install-Facebook-pixel/m-p/890683#M197882