You can check out our demo account report Issue Days in Backlog, we use measure Days in transition status till now there that you can copy and use in your report.
The formula is this:
-- days in transition status when issue was in this status in previous times
Cache([Measures].[Days in transition status]
-- days since last transition to this status
IIF([Transition status].CurrentHierarchyMember.Level.Name = "Transition status",
[Transition status].CurrentHierarchyMember.Name = [Measures].[Issue status], 1)
[Measures].[Issues history] > 0
[Measures].[Issue status updated date],
And then you can filter your report by Transition status category (In progress and New) to see only not completed issues.
Gerda // email@example.com