Cite a permanent or ongoing museum exhibition the same way you would cite a temporary exhibition, but in most cases omit dates since there is no closing date, and the opening date may be unknown.
If an opening date is known, list it in the “Publication date” slot, followed by a hyphen and a space, as shown in the following example:
Epic Abstraction: Pollock to Herrera. 17 Dec. 2008- , Metropolitan Museum of Art, New York.
Published 4 December 2019