Problem:
pgAdmin ist not starting twice up to version 4.3.
This is very annoying if you want to develop professionally.
Solution:
The new version is runing as a web APP.
If you now the URL, you can open the web app twice.
Open the pgadmin menu FILE / RUNTIME / VIEW LOG ...
In the log we can find Application Server URL: ...
If you copy the URL into the local browser, a new instance will open.
Happy coding
Note:
I have seen screenshots from Mac with a menu named "New pgAdmin 4 window".
Unfortunately, I could not find this menu item under Windows.
The tip that I also found, to perform a port scan, seems a bit more complex and not very practical to me.