The System variable XCLIPFRAME toggles between visible and invisible XClip boundaries. Being 0 for invisible and 1 for visible. Some important points to consider are:
- the Xclipframe will show on the same layer as the XREF or Block is.
- Xclip frames inside Xrefs will appear in the drawing regardless of those Xrefs having other Xrefs as overlays or Attachments. And there seems to be no way to modify that.