In 11 fl octy i would like to set the alarm "beep beep" chirp a bit louder, not the horn. It gets quieter every time, or just my ears. Is there a way in vcds?

I suggest your alarm has a failing battery or sounder and may need replacing. 

Skoda say service life is six years. Typically they last a couple of years more which is where your car is now.

A normal alarm horn is more than loud enough, even too loud.

 

The loudness cannot be adjusted.