The error log is a view against the SQL database table SysErrorLog. It actually is for the most part only interesting to developers or to find an issues within the application.
Almost everywhere within the source code is an error handling implemented, at least the module/form will be processed by the error handler. You can add additional values in the code to have better insight where exactly an specific error happened.
For a more detailed example have a look at the mdlLDAP / module – you will see additional information like Const ErrProcdure per function or sub procedure are set by a const string – there is even a Dim ErrSection As String in there that actually can help you to narrow down the part of the procedure in an hunt of an issue.
The information then will be written to the SQL database – of course assuming that there still is an connection. I did not implement an additional write to local error-log or similar, since I did not have a use for it yet. You sure could just change the mdlErrorHandler and adjust this to your likes.