Target frame:
/run C_CVar.SetCVar("showTargetCastbar", "1", "SHOW_TARGET_CASTBAR")
or for arena enemy frames:
/run C_CVar.SetCVar("showArenaEnemyCastbar", "1")
Target frame:
/run C_CVar.SetCVar("showTargetCastbar", "1", "SHOW_TARGET_CASTBAR")
or for arena enemy frames:
/run C_CVar.SetCVar("showArenaEnemyCastbar", "1")