Hi darek,
It's not enough because you cannot use comments variable in ST (or I don't know how to use it?). When you program is biger you have to think what the marker means. Of course you can comment all the lines of code, but when you change something you heave to change all the comments. That's terreble.
Sorry that I have to say this, but what you want is an PLC at the price of a VW with the comfort and functions of a Mercedes.
If you want to program with symbols, there are also Eaton controllers that can do this, e.g. XC-100, XC-200 or XC-300, with Codesys as programming software.
But you have to pay a little more for this.
By the way, the easyE4 with easySoft is, as far as I know, the only small controller that even offers ST as a programming language.
Neither Siemens LOGO!, Schneider Zelio or Crouzet Millenium offer this.
BR
Ralf