The standard accesskey for saving an edit on Wikipedia, and indeed for posting messages in forums across the web, has always been Alt+S. This doesn't work in Flow.

It should be a very simple fix, just add the attribute accesskey="s" to the "Save" button. (Or, well, instead of "s" it needs to use the content of {{int:Accesskey-save}}, but for y'all that should still be pretty simple.)