Stems across staves

Someone told me how to extend stems across staves, but I've forgot and can't guess it either. I thought it used to be highlight stem, shift +, then move the stem into the next stave.

Would you be so kind as to tell me once again, and tell me where it is in the 4.0 handbook? Maybe if I see where it's written I'll be able to find it again.

You can tell I'm preparing to forget again.... ;)

Thanks! <3