Add a "Save" button to the main toolbar
In a program like Scrivener, saving---as the kind of action one takes periodically with a text editor or word processor---isn't something one ever has to do, except in rare scenarios. Instead, Scrivener works more like OneNote, or even iTunes, in that it manages a large collection of files (a project is more like an iTunes library folder than a file), and everything you do with and to those files is automatically saved as you work.
The concept of having a button on your toolbar that saves would in most cases perform no real task when clicking it. By the time most people manage to reach for their mouse, position the pointer over the button and click it---everything they would have done recently has already been saved.
The only major difference between iTunes and Scrivener, at least in this one specific regard, is that people don't expect to have to save an iTunes database.
So with that known, the question becomes: how well can I protect myself from myself, if the only copy of my work is constantly saving beneath my fingertips? We have a few tools that you can use to protect your work:
Snapshots: it is very briefly covered within the Interactive Tutorial, from the Help menu, if you are unfamiliar (and a brief is all you'll need, it's quite simple). It's a bit like using "Save As", but without all of the distracting bits of choosing where to save and what to call it---just press
⌘5on a Mac or
Ctrl+5on Windows (or add a toolbar button if you prefer) and you keep writing; no distractions, you can even do it from Composition Mode, where there is no interface at all but your text.
Project backups. In the toolbar customisation panel, you'll find a "Back Up Now" button. If you aren't familiar with these, basically for every project you work on, Scrivener by default keeps six of the most recent copies of it on hand. With settings you can bump that up to 25 additional copies (or no cap at all). These are whole copies of your project, in each phase of its development.
Point being: if you want to save, the Back Up button is the way to really do it. That not only ensures your current edits are all written to the disk (which most usually are) but it ensures a second copy of that project is created, with every detail preserved down to where your cursor is blinking. I recommend visiting the Preferences: Backup pane and making sure those settings look good for how you work; the more backups the merrier, and especially if you make a habit of clicking that button.