already used video - setting

hello everyone!
I know that it is possible to see that some audio or video is used twice or more in a sequence. I have that setting on my computer at work but not at home, which is very irritading to be honest - its a very useful feature.
So to cut it short: where can i find that setting? I already tried to use that meta-thing but then I can only see it in my project window, not on my sequence.

thanks a lot in advance to anyone for helping and kind regards from Italy!