I have a customers detail view with things like their name. At the top there is a toolbar where they can save, reload, delete etc...
On of the properties they can edit is a list of phone numbers. When someone adds or deletes or edits a number. Should this be automatically saved or should it be saved after the users clicks save on the customer itself?
Be consistent throughout the interface.
If you have a save button related to the entire "customer detail view", then the save button should be used to save all information under it. To prevent errors of unsaved data, you can show an alert when the user changes data and tries to leave the screen.
However, I would argue that auto-saving is becoming an expected feature of web applications.
Related: Guidelines for when to auto-save settings vs "save" button and When to save data?
