Access the Xref Manager: Type XREF in the command line and press Enter.
Select the Xref: Choose the Xref you want to modify from the list.
Modify the Path: Click on the Path Type and select Make Relative. This ensures that the references will correctly point to the ALT-1_Xrefs folder relative to the current drawing location.
References:
* AutoCAD Help Documentation on Attach and Overlay External References