Tb Android: Opening msg action changes it to read

Long time user of Tbird on Win and now Linux desktop. I have it set up so that reading/opening a msg leaves it's status as unread. I use read status in the msg list so that I can tell what I have dealt with and what is still to be actioned. With Tbird Android, which I use as well as desktop, reading or opening a msg turns it's status to read and it then gets lost among other msg on both platforms. Can't find a setting to change this so that both platforms act the same. Or a workround/change in my workflow.