New Soundfont, VST Instrument in V4 without Synthesizer???

Regarding to the Guy who has mentioned that the V4 Musescore has no Synthesizer, i would like to ask how i can include a new soundfont or how i can include a VST Instrument? This is really important. I do windmusic, but there is no sound for realistic Flügelhorn. It is just the same than the trumpet sound, which is ridiculous. The easiest way would be, that musescore includes a realistic Sound of a Flügelhorn, or gives a chance to include new sounds or VST Instruments. Isnt that a big bug?