using MUI, how can I create an installation with section info box on bottom, not left

as NSIS installation itself

both
!define MUI_UI_COMPONENTSPAGE_SMALLDESC
and
!define MUI_UI_COMPONENTSPAGE_NODESC

do nothing, did I miss something else? there are no examples with interface styles at all 🙁

and, the second question - installation has a lot of sections, and total size is huge, has anyone a script that could show sections' and groups' sizes together with names, as MSInstaller for example, so user don't have to click all sections to find out which of them have a big size?

I think you need, either change the UI.exe source code or open it with resource hacker to modify the controls.

Also try MUI_COMPONENTSPAGE_SMALLDESC

Thanks 🙂

MUI_COMPONENTSPAGE_SMALLDESC works fine! 🙂