[Qt-creator] How to remove big buttons on the left side of the screen?

[George Brink]

My netbook has only 10" screen and I prefer to work in full screen mode 
with the hidden Sidebar. I press Alt+0 only when I need to choose the 
source code which is not opened yet...
But I still cannot get rid of a huge, annoying buttons "Welcome", 
"Edit", "Design", etc... I never use them (hot-keys are much faster) and 
they take precious space on the screen.
How to disable them?