How to reproduce:
1. Create a new Unity project, set its Graphics API to "Direct3D12 (Experimental)" and close it
2. Launch NVIDIA Nsight Graphics 2019.6.1.0 and open the attached project "1203035_testnsightproj.nsight-gfxproj"
3. Double-click the project in the Project Explorer panel to open the "Connect to process" window and navigate to the "Launch" tab
4. Set "Application Executable" to a directory where Untiy.exe is located (e.g. D:/UnityVersions/2020.1/2020.1.0a17_ccc6f9131a63/Editor/Unity.exe)
5. Set "Command Line Arguments" to "-projectPath "x"" where x is the directory to the Unity project
6. In the "Activity" tab below the "Launch" tab, select "Frame Profiler" and select "D3D"
7. Click "Launch Frame Profiler" and once the Unity project is opened, enter Play Mode
8. In the new Nsight window, click the "Capture for Live Analysis" button below the menu bar
9. Inspect the Range Profiler View

Expected result: Perf Markers appear in the Range Profiler view
Actual result: Perf Markers are absent if the Graphics API is set to "Direct3D12 (Experimental)"

Reproducible with: 2017.4.35f1, 2018.4.15f1, 2019.2.17f1, 2019.3.0f4, 2020.1.0a17

Note: if in the first step the Graphics API is set back to "Direct3D11", the Perf Markers appear in the Range Profiler View (as seen in the screenshots)