For Visual Studio 2015, You can enable a "partial" intellisense by opening the Xaml page with the Source Code (Text) Editor.
It's not perfect, but most are Working.
Now I've installed Visual Studio 2017, and I'm totally unable to activate this (important) feature.
I've tried different editors, but without any luck (that is intellisense)!
Do I have to install a special component, or are the feature missing from Xamarin?