Today I happened to try the SEarch command with no argument in XyWrite 4, and made this little discovery: it restores to the CMline, and executes, the last-used SEarch command. A handy feature, yes, but it's also heartening to find out, after all these years, that a bit of the iceberg still lies beneath the surface, waiting to be revealed.
Another nice Xy4 "no arg" command, which I think was identified here a long time ago, is CD. This switches back to the last-used directory; executed repeatedly, it toggles between the two directories.