The Backlog column in Codetree, in my mind, is broken.
If I go to Task Board in a milestone, the Backlog column (which I can now choose to not display, thank you), but it shows all tickets - not just the tickets in that milestone. They are ordered all over the place, and you cannot actually see what is in the milestone (Sprint).
This column should show all issues assigned to the milestone that are Open, with no label putting them in a defined swim lane. The issue number at the top implies that is all that should display - but all issues are displayed.
To deal with this, we had to define another label (ugh) called Planned. My concern about this is that if any ticket ends up in that milestone, but not with one of those labels defined, the issue will disappear from this view, simply by someone changing a label and accidentally marking it to be a status we have not defined to show in a swim lane.
So - please make the Backlog column in a milestone do what it is supposed to - only show the Backlog for that milestone, not everything.