We recently added auto complete for MBS function names for 12.1 pre-release, which is really handy. Just type the component name and once you got the right one, maybe with cursor down key, you can press the dot to complete. Then you continue to type and a new auto complete list shows the function names:
Once you got function name and there is not much text following, the MBS FileMaker Plugin will add the parameter names as placeholders. You can directly put in variables with same name or enter some value there.
Available or recent FileMaker versions on macOS in MBS FileMaker Plugin 12.1.