The idea is that right clicking on the Don't Reselect Unit button undoes the last selection. So it would cycle through all units selected that way in reverse order and also undo the "don't reselect part". This would put the button more in line with other parts of the UI where right clicking can be used to cycle a button in reverse order such as the unit selection button and the deployment inventory tabs. Optionally you could also add a feature to middle mouse click the Don't Reselect button to undo all of the selections at once.
Sometimes I hit the Don't Reselect button by mistake when trying to switch to the next unit, this would provide a way to undo that. Another common scenario is that I'm using the Don't Reselect button to "clean up" a bunch of units that have no TUs left but I click the button one too many times and have to go back and search for the one I just "deleted".
