Open an external file from within Scrivener (in my case, it’s a Scapple file I nested under my Scrivener ‘Story Lines’ folder)
Modify, save and close said Scapple file
Save Scrivener project (note that prior to saving, the menu bar doesn’t have the ‘*’ so it doesn’t seem like Scrivener recognize that changes have been made)
Close Scrivener
This issue only occurs if I DO NOT modify any other internal Scrivener files. It seems like Scrivener doesn’t recognize that changes have occurred and therefore doesn’t make a backup file. Otherwise, if I DO make other changes within Scrivener, the backup occurs and all the files (including my Scapple file) are backed up correctly.
There are indeed certain actions that will not cause a backup to be triggered through the normal means—most of them intentional; for example you probably wouldn’t want a new backup created simply because you clicked on a folder, even though technically speaking that modifies the project (setting the last viewed item, adjusting history queues, etc.). In this case, if it is anything like on the Mac, it’s more of a technical issue in that the software is largely “unaware” of the state of files it cannot work with directly. The modification date that is stored for the item only tracks actions taken within Scrivener upon that item, such as adding a keyword or changing its name.
So just be mindful of that, and use the File ▸ Back Up ▸ Back Up Now command for those cases where nothing has been done to the project itself but you know you’ll want a backup of it.