So 'All files' button is missing for me in SP Designer. I checked here but my admin says he can't see any sharepoint designer settings - he can just enable it. Is it a limitation of Office 365 we're on that you cannot do it? Also i found information that one needs to be a whole site collection admin to actually get 'all files' unlocked. Anyone knows if its like that?
I can confirm All Files appears just fine on Office 365 sites.
I think some of the links/options in there are security trimmed and will only appear if you are a site collection administrator.