If you open drawings and want to know if there are any XREFs in the drawing, you do not need to open the XREF manager. Simply look at the bottom right corner of the screen in the status bar. If a button appears with a piece of paper (document) and a paper clip (as shown below) the drawing does have XREFs.
You can click this button and it will open the XREF Manager. It performs the same function as using the command XREF <enter> or the alias XR <enter>
Shown below: XREF manager: