It’s always a good idea to add the currently used kicad version to your questions/issues, so we can give better answers.
v7.0.x (current kicad stable versions): there will be no enhancement and you have to live with that restriction
v7.99 (currently development version, will becoming the next v8 version): the BOM-export from the symbol fields table was already enhanced. It includes the option to choose the character used as field delimiter: