Please Steinberg,
when closing an active project, the de-activated project window in background must not be opened automatically because, probably, we don’t need to open it again. If it’s a huge project, it needs to wait all the plugins and libraries loading for no reasons! Let the user choose to activate the project or just close it. It’s a longtime waiting feature, we reached v. 10 and nothing yet. Thank you, very much appreciated.
seem like this was just implemented in the latest release of Cubase 10.5
Really? Wow finally 
Thanks for the news, I’ve just read yesterday about the new 10.5 version.