Psalm 60's title says Joab struck down Edomites in which valley?

Answer: The Valley of Salt

The title recalls when Joab returned and struck down Edomites in the Valley of Salt.

“For the choirmaster. To the tune of “The Lily of the Covenant.” A Miktam of David for instruction. When he fought Aram-naharaim and Aram-zobah, and Joab returned and struck down 12,000 Edomites in the Valley of Salt. You have rejected us, O God; You have broken us; You have been angry; restore us!”— Psalm 60:1 (BSB)