The LibreOffice supports many programming languages to call the API functions and procedures of the LibreOffice.
There is not (never was and never will be) a full compatibility between the LO API and the MS Office VBA.
The MS Office VBA is a "programming language + programming environment + a function library" in one.
The function library of the LO (read: the API) is fully independent from the supported programming languages and programming environments.
The StarBasic and the built-in IDE (the most obvious programming language and environment of the LO) is only one of the programming tools to call the API functions. You can call the API functions from Python, JavaScript, etc...
API: Application Programming Interface.
Always, it's better, migrate to LiboBasic. Yes, thousands of lines of VBA code too.
Is there a manual available? One that would describe the programming environment and perhaps have a word or two on converting VBA code to LiboBasic. Maybe it would also contrast the two, VBA 7 LiboBasic.