The final stop for Europe’s first major Marina Abramović retrospective, which opened in Stockholm in 2017, is Belgrade, the birth city of this boundary-breaking performance artist. From paintings and drawings to audio works, films, and re-performances of past pieces, “The Cleaner” presents a rich study of Abramovićs work over half a century. “What you’re doing is not important,” Abramović wrote in her 2016 memoir, Walk Through Walls. “What is really important is the state of mind from which you do it.” —J.V.