Before reporting to Microsoft I want to ask here. I have a problem that I cannot see Live Visual Tree of my WinUI 3 application. I cannot even see the in-app toolbar. I can see both in WPF and UWP application, no problems. I have these options for hot reload, that should be fine.
I am using VS2022 17.3.1 and Windows App SDK in version 1.1.4. Weird is that it was functioning without problems, but one restart of application just broke that. I also tried adding the ENABLE_XAML_DIAGNOSTICS_SOURCE_INFO to environment variables manually, but no luck there.
It seems that 32-bit WinUI 3 app is working fine, it only affects 64-bit WinUI 3 applications. Even the new and blank ones. Packaged/unpacked type doesn't affect the problem.
I tried uninstall and install VS again, no changes.
So I did finally find a solution (more of a workaround) to this.
Run following commands in elevated cmd, where you replace WindowsAppRuntime version with version you currently have (for me it is Microsoft.WindowsAppRuntime.1.1_1004.584.2120.0_x64__8wekyb3d8bbwe):
takeown /f "C:\Program Files\WindowsApps\Microsoft.WindowsAppRuntime.1.1_1004.584.2120.0_x64__8wekyb3d8bbwe" /r /d y
icacls.exe "C:\Program Files\WindowsApps\Microsoft.WindowsAppRuntime.1.1_1004.584.2120.0_x64__8wekyb3d8bbwe" /grant Users:(RD,R,REA,RX) /t
Don't know what it does, but it is working. This solution is taken over from Developer Community
UPDATE: You have to repeat this procedure when you update Windows App SDK to a new version.