How do I prevent the workspace from closing when I close a document?

I'm currently running v18.3 on Windows. I would like to keep my selected workspace visible at all times. When I close a document, the workspace also closes. This is a new behavior that started when I upgraded from 16.4.3 to 18.0. (My company normally updates InDesign every two years, due to the need to update extensions.) Additionally, every document switches the workspace to "Essentials" when opened, unless I changed the workspace with the file open and resaved the file. 

Is there a setting somewhere to force the selected workspace to remain selected? I guess I can add an event listener to set the workspace on every document open and close, but that seems like an unnecessarily brute-force approach. Plus I would prefer to be able to change the workspace manually at times and have that workspace remain selected until manually changed again. 

Any ideas?

Thanks!