You need to generate an aggregation for it with the option of “Define new calculated member”
You can see the link inside the “Sprint” Dimension:
Add the name you want and the code of:
Aggregate(
Generate(
-- get all boards
[Sprint].[Board].Members,
-- access all children - sprints from the board and get the last closed
Tail(
Filter(
[Sprint].CurrentMember.Children,
[Sprint].CurrentMember.GetBoolean("Closed")),
-- 1 last (from Tail) closed sprint from a board
1)
-- address the first (0) member from a set
.Item(0)
)
)