Hi Lex_from_Belarus, What you mean by adding a "silent installation"? There is an express installation function and also there is a silent/gaming mode in the avast settings. ::)

I mean install process when I don’t see all windows of installation step and don’t participate in this process.
Example:
avast.exe /verysilent
OR
avast.exe /silent
OR
avast.exe /S

How I can run silent instllation?