How to present ‘Save All’ button on long configuration screen?

We have a large (long) screen with a lot of account configuration controls. Currently each change is automatically saved as soon as it is made, but Engineering wants to change this (for apparently good reasons) so that the changes are accumulated throughout a session and saved in a single save event at the end.

My idea is to have a 'Save All Changes' button appear as soon as the first changes is made. There is a what I call a utility section in the top right of the screen, where several high level actions and stats are made available via cards. This would make a logical location for such a button.

My problem is that if a user scrolls down the page and starts making changes below the fold (as they are quite likely to do) they won't notice the button appear.

If they try to navigate away they'll see a warning that there are unsaved changes on the page, but I'd obviously prefer to help them avoid this.

How can I provide a way of saving all changes on a long screen like this, in a way that is clear and obvious.

^{download bmml source – Wireframes created with Balsamiq Mockups}