This Git contains all document-level JavaScript that is used in the AcroForm PDFs called MPMB's Character Record Sheet. Note that you can't create the PDF from just this repository, this is just the JavaScript used at the document-level.
The _functions folder contain the document-level functions that the AcroForm utilizes. These are called from form fields, buttons or bookmarks.
The _variables folder contains all document-level variables that the AcroForm utilizes. Here the sheet stores the information that it uses to populate the fields.
The additional content folder contains scripts that can be imported into the sheet using the "Add Extra Materials" bookmark or "Import" button. Each file is a complete script. You can add multiple files, but take note that they will be processed in the order they are added.
The additional content syntax folder contains explanatory files for making the additional content scripts.
There is a community of people who actively make additions to MPMB's D&D 5e Character Tools over at the /r/mpmb subreddit.