Can someone point me in the direction to the full documentation of predefined styles contained within the ubiquitously referenced /assets/notifications/styles.css file within the Notification(s) section under Settings?
And if there is no such full documentation, why not? Why is this not fully documented?
What is within this specific file will vary from theme to theme.
CSS, when well written (which is the case of all official Shopify themes), is documented by itself - by having an understanding of HTML/CSS it's clear what every piece of code does once you read it. Especially if one is using some sort of architectural paradigm or naming convention, like BEM. Unless one's building a framework I don't see any need to document CSS, it would be redundant and, therefore, not useful.
What has lead you to question this, are you trying to achieve something specific?
The styles in question are not associated with themes.
It (/assets/notifications/styles.css) is referenced by the notifications templates in the Notification(s) section under Settings.
By examining the notification templates and making note of the classes used within them and comparing them against the inline-css that get rendered automagically by the shopify API I can tell there are some stock standard styles.
It would be helpful to know what exactly has been boiled in by default. So that if I need to override or recycle/reuse styles it's not an absolute waste of hours of my day.