As i found out quite simple - just to edit Word.qat. Next step - to add own icons. Playing with custom UI editor and still not clear how can i change built-in mso on my own

Greg Maxey's pages give examples of doing this. First there is a host of available icons built into Word (although not in the modify the QAT dialog). These are easy to add if you know their names by modifying the XML for the QAT. Otherwise, you have to add the icon to a Ribbon Tab (perhaps not displayed in final production) and copy them from there to the QAT.

I'm glad you find it simple. i find it a pleasant puzzle to work out; but then I'm a lawyer, not a programmer.