LibreOffice uses VBA (Visual Basic for Applications) as its internal "macro" language. As of version 6, the IDE does not yet appear to support the auto-fill features of Microsoft's VBA implementations.
Probably the best place to look for VBA usage is in the Handbook for whichever component you are using, but I have not verified this.
Much of the web-formatted documentation appears to be available only as static files which are installed with LibreOffice:
/usr/share/libreoffice/help/en-US/text/sbasic/shared/main0601.html: LibreOffice Basic (General) Help – API documentation, including both VBA and Python
/usr/share/libreoffice/help/en-US/text/shared/optionen/01130100.html: VBA Properties – "Specifies the general properties for loading and saving Microsoft Office documents with VBA (Visual Basic for Applications) code."
- Apache OpenOffice BASIC Programming Guide: LibreOffice's docs link back to this for more comprehensive documentation