Startup-Scripts
JS-Engine supports startup-scripts, similar to the CSS-snippets from Core-Obsidian.
You can select the script-file you want to use as startup-scripts and JS-Engine will run them for you when never Obsidian starts up.
Configuring Startup-Scripts
You can configure which files you want to have run from JS-Engines settings tab.
Global Variables
JS-Engine runs the scripts in the same context as all other code-blocks. So the available global variable are the same and can be found here.