I think Q DISK (QUERY DISK) should show you all the minidisks attached to your machine. Perhaps the ISPF only attaches when you go into it and detaches afterwards (common way to do it). You may be able to "drop out" whilst in ISPF, by entering CP or CMS, you might even try PA1, which should allow you to enter commands at a CP prompt. Without "dropping out", just CMS Q DISK on the command line might get you there. If you see something likely-looking, you can CMS FILELIST minidisk to get a look at it. When you "exit" after finishing, you should be back where you started in ISPF.
However, things may have changed since I last used VM - err, that would be 1989
XEDIT is highly customisable. Took about a day for me to make it behave like the ISPF editor. XEDIT macros just had a type of XEDIT. Type of EXEC for "execs", could be written in EXEC or EXEC2, CLIST-like things - I'd like to think they're not still around, but I suspect they will be. Prefix with CP to run a VM command (Control Program), with CMS to run a CMS command/exec.