I can only imagine what 60 workspaces looks like on the Inquires menu.

My largest list is about 30.
Only GVS workspace files are listed on the Inquiries menu, not any of the individual GV files. So if the purpose of looking for GV views not attached to a workspace is for making the Inquiries list shorter, then you don't have to pursue this as removing GV files will not make the list shorter.
If this is for a general cleanup, there is no 'automatic' process to see which GV views have been referenced in a workspace. What I do (which I confess would be time-consuming for a list as large as yours) is to open each workspace in the list, re-save the workspace, and then close, and choose to save each view in the workspace. This will update the file date for the GVS workspace and all GV views. After the list is completed for opening, saving and closing, any GV views not belonging to a workspace will not have the file date updated, and looking at the files in Windows Explorer sorted by Date Descending will have these at the end of the file list.