I've been using LXDE for a month and newly I've realised that not every option included in LXDE interface. for example, when I start ubuntu with default unity interface, everything is normal. but when I open with a lighter interface which is LXDE, for example, I can't find "startup windows" tool anywhere! or I could not find "shortcuts for keyboard" . or I could not find any "screen lock" options. I found something like a screensaver but it does not include everything I need.
So I must ask that is there anything I missed about downloading this lighter interface? should I download more stuff to be able to use every general ubuntu software and tools? if so, what are they?