Adding a New Scene Additively from Scene Template Window while having unsaved scenes in the Hierarchy doesn't prompt with a Save Scene pop-up and removes all the scenes added additively.
Refer to the attached Video.

Steps to Reproduce:
1. Create a New Project
2. Project > Create > Scene (2-3 times)
3. Project > New Scene > Drag to Hierarchy (repeat for all new scenes)
4. Ctrl+N > Basic(Built-in) > Load Additively > Create
5. Repeat Step 4

Actual Result:
All additively opened scenes are removed due to one Untitled scene

Expected Result:
'Save Untitled Scene' pop-up window should prompt the user to Save, so that a New Untitled scene can be created and loaded additively

Note:
Scene Template Window was introduced in 2020.2.0a15

Reproducible with:
2020.2.0a15

Workaround:
Scenes can be additively added or created from
1.Hierarchy > Scene > Burger button or Right-click or
2.Dragged from the Project Window

Environment:
Windows 10 and macOS 10.14

License type: Pro