Alright, I have to chime in here.
(I've been an indie software developer for 40 years.)
I am currently playing a game built with Visionaire Studio.
I play on a Mac.
On a Mac, it's very normal to quit any program with cmd-Q. Yes, maybe Alt-F4 is not the usual way to do that on Windows (however, I do that there often as well).
But on a Mac, it's what nearly everyone does to quit an app.
Imagine my surprise when I learned that the game lost many hours of progress (because it didn't autosave either).
So I look here, search the forum for "quit" and find this. Where the developer(s?) do not even understand the need for catching cmd-Q and providing a hook for it, even though users ask for it.
Let me give you some reasons why being able to catch an app quit event is needed:
Windows or MacOS may decide to restart the computer, e.g. to perform an Update. Then the OS will ask every app to quit - and the app gets the opportunity to save their data or even cancel the quit if necessary. This engine doesn't do either, it seems.
Or imagine that the user put the game into background, or video call came in and the game ends up in the background. If this takes a while before the user goes back to playing, now the user may have even forgotten that the game still runs in the background. And maybe the computer says it wants to install an update or that the memory gets low and some programs should be quit to free memory. And boom, once the OS asks the game to quit, again all progress in the game is lost.
This leads to frustrated users and eventually to angry, negative, reports, which will hurt both the game and this engine.
So, please add proper quit events ASAP. Or, even better, also add a "Should save now" event, which you invoke whenever the app goes into background or is quit, in order to GUIDE programmer who do not expect this, into learning to do their autosave when they get this event. Because that way, you control when the app should save its state and the user of your engine doesn't have to think about all the cases where it's probably a good idea to save.
The fact that even you, the designer of the engine, didn't think of providing a hook for save-on-quit is a good example of the unexperiedness that exists here - and if you couldn't even think why that's necessary, then the game devs might even less think of it - so please remind them by adding approriate hooks and document why they should use them, please.
If you need help specifically with macOS - I can perhaps assist you. You have my email.