I emailed Toby R about a possible update of MM_Preloader.
By the way, I think you are wrong and MM_Preloader can actually preload items which aren't on target layout. Just use "Add object", start preloading and you can preload any object from the project. Tell me if I missed something but I'm quite confident that's how it is working.
No, I am not wrong. I used that addon a lot of times and used all the possible combinations I could think of. What you are referring is a workaround, which is messy as it includes the use of a Global Layer and both side of layouts that have to handle it.
I already replicated the MM_Preloader through events except the Get Object Class from the target layout. It is actually more responsive and preloads faster through events.
As I said, TobyR knows he can't port it, he already said that. Well, at least he can't do it without doing some hacks, which he knows is not recommended in a volatile software like Construct 3. It's not recommended by the Construct Team.
Although, as I said, you can make a basic version of the MM_Preloader currently with the SDK, just without the Get Object Class from another layout. But that is not ideal, you can just make it through events and you'd have a more responsive effect. And that is just a workaround in the first place, not the real preloader support.
What I am suggesting is a better solution to MM_Preloader. That does not only let us preload objects from a target layout but also introduce and preload a new object to the target layout.
And this isn't a experimental thing. Most Game Engines have some kind of support for this since it is supposed to be a basic need for asset loading. But Construct seem to have missed this because of the layout-by-layout preloading, which was suppose to solve everything. But didn't take into account larger and dynamic grouped assets.
Oh no... These addons are such a mess in the long run! :(
No SCML, no LiteTween, no MM_preloader, none of Rexrainbow's addons...
Hopefully someone will show up and port these.
Not really... The SCML plugin is not a problem since it can be ported soon. Some of Rexrainbow's addons are compatible and can be ported to the C3Runtime, a lot are already ported. And we have a few Tween plugins for Construct 3 Runtime.
For example, Tweeen : https://www.construct.net/make-games/addons/163/tweeen