Hi Tudor,

re:
> by side panel I understand as object browser panel or commandUi panel

If you set up the script mentioned above (http://kyticka.webzdarma.cz/3d/moi/#MaximizeViewport)
on a shortcut key, then it would be possible to maximize and unmaximize viewports without using
any other UI.

If you mean you want some way to hide all the regular UI panels, try this one:
http://kyticka.webzdarma.cz/3d/moi/#FullScreen

If neither of those is correct I will need more details about what you're trying to do.

- Michael