Either i don't really understand this request or i am kind of against it.

If you are actually talking about the save button of normal content elements, i am against it.
In many text editors you have the save button at the top left corner at a fixed position,
so the current state is not something that is unique or new for an editor.

I disagree that the button is closer to the change and there is less mouse movement,
as that solely depends on the length of your form.
If you have created your own content element which has more input fields than usual,
it is easier for the user to have a fixed save button at the top rather than to have to scroll to the top or bottom of a form.
Also the button wouldn't be visible at the bottom if you have really long forms, since you would have to scroll to the bottom.
And in order to avoid such issues and buttons at multiple places, i think the current solution is great.
We must consider mobile views as well since the backend is responsive now.

'People fill out forms top down' - this might only be the case the first time a form is created or edited.
When one only wants to change a small thing, that behavior is not necessarily the case.

I don't think one can compare a shortcut like <CTRL-S> with a button.

In addition to that we have more places in the backend, like the page or list module in general, where you can find action buttons like view, edit or add in the doc header. Thus looking for a save button at the same place seems legit to me.

Besides that, we are already checking whether the user is closing a form with unchanged saves,
so i don't really understand how changes get lost so easily.

If i misunderstood your feature request, you can gladly ignore my comment :).

There has been no feedback since 90 days,so I am closing it for now.

If you think that this is the wrong decision or you want to add more details, please reopen it or open a new issue with a reference to this one. Thank you