This functunality went away how to get it back?

It was there but is not now.

In Windows Explorer or in the SOLIDWORKS Task Pane File Explorer, right-click a SOLIDWORKS document and select SOLIDWORKS > Rename or Replace.

How do I get it back?

SW2017 SP5  Win 10

function exists in "SOLIDWORKS Explorer"

SOLIDWORKS Replace on the Mini Toolbar.

But I always used it from "Windows Explorer"

SolidworksGeneral