There's no button (that's a gap on my side, not intended behavior). New Project currently goes only through the folder picker, so on Firefox or Safari it just stops there. The virutal filesystem fallback is only in Open File, which is also why zahrevsky's workaround gets you in.
I'll make New Project also fall back the same way, so it works in Firefox and Safari without the detour.
I'll make New Project also fall back the same way, so it works in Firefox and Safari without the detour.