GM Launchbox

Launchbox is a GameMaker library for scheduling and running initialisation tasks.

The package to import into GameMaker project is available for download as Launchbox GMS2 Package (YYMPS).
A web demo is available, showing some basic functionality.
There's also a downloadable GameMaker project: Launchbox Demo Project (YYZ).

You can learn more from the documentation on GitHub: https://github.com/Alphish/gm-launchbox