Hi,
There is a possible solution that you can try. Since you want half of the files in one window and the other half in another. You can first open half of the files in the editor and then undock the editor. To undock the editor, click on the dropdown arrow in the upper-right corner of the editor window and select undock.

It will keep all the files in one window. Now you can open the other half of the files and do the same steps.
This way you can open 50% of the files in one window and the other 50% in a separate window.
Hope this will be helpful!