Android Studio Merge Windows. (Open multiple projects in the same window)

How to open mutliple projects of Android Studio in the same window using tabs?
Most of the questions I check have the classical option that takes you to File -> Appearance -> System Settings where you have to choose between opening new projects in the same window or completely new window.

I already have information about it. I want multiple projects in the same Android Studio window then navigate between them with tabs.

1. Choose "Open project in New window" setting:
   

2. Open another project (will open in a new window)

3. Choose "Merge All Project Windows" from the Window menu:
   

The confusion comes because merging windows has been introduced later than opening the projects in one or multiple windows feature. I will try to clarify below

Opening Android Studio projects in ONE window means that once the user hits File -> Open the current project would dissapear and the window would be filled with the newly opened project. This can be achieved by doing:

In the project settings. (Settings -> Appearance -> System Settings).

Having this configuration as in the picture would mean that by default you CAN'T open different projects in the same window using tabs.

Opening different projects in the SAME WINDOW USING TABS, or in other words: Merging Windows in Android Studio/ IntelliJ, can be achieved by doing: Window -> Merge All Project Windows. But in this case you should have at least two separate project WINDOWS at the same time opened on the screen, otherwise the menu would not be responsive. See the image below: