"Open Documents" sidebar doesn't open in external ("New Window") editor

The "Open Documents" view in the sidebar allows to change between documents on the currently active Editor Split. However, this doesn't always work when the Editor belongs to an external window, as created by the menu Window -> Open in New Window.

Initially the functionality works for these kind of windows, however as soon as the Editor in the main Qt Creator window gets activated, the external windows lose the ability to change between documents by using the Open Documents sidebar.

How to reproduce

1. Open a project consisting of several files. The Editor is now empty.
2. Open a New Window: Window -> Open in New Window.
3. With the new window selected (ie. focused), open several of the project's files. All files are opened in the external window.
4. Switch between opened documents by using the Open Documents sidebar. The Editor in the new window switches correctly between documents.
5. Click on the main Editor to make it the currently active.
6. Switch between files again just like previously. The Editor in the main window is now showing those files.
7. Click on the new window's Editor to make it the currently active.
8. Switch between files again just like previously. The files are opened in the Editor from the main window, which is incorrect.

Expected behavior
Expected to see the documents being opened in the external window's editor during the last step, instead of being opened in the main window's Editor.