Hi Daniel,
In my understanding you are trying to open multiple files (tabbed in multiple editor windows).
I was not able to get two different undocked windows with multiple tabs from MATLAB R2015b back until R2012b. Only the primary window has tabs and rest of the files open up in a separate new window(and not tabbed on the parent).
However, I have noticed that we would be able to open multiple editor tabs when the view is set to "Left/Right" mode(or any other mode than "Single"). You may undock the whole "Editor" pane from MATLAB to another window as well. Please refer to the screenshot.
I hope this helps.
Thank you,
Adithya
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