title: Structure guidelines not showing in some XAML editor windows
body: <p>VS Pro 2019... I have two sessions open, different projects, each with some C# and XAML code tabs, problem is in one of the XAML editor tabs..</p>
  <p>In one window, XAML structure guidelines are shown... in the other window - not.
  Yes I have checked the Options/Text Editor/General/Show structure guide lines... it is definitely checked in BOTH windows.</p>
  <p>In the problem session, I get structure guides shown in my C# code tab just fine... but the XAML tab refuses to obey the checkbox.</p>
  <p>I'm stumped as to why...</p>
  <p>Thanks in advance for any help</p>