Zaddikim  
The heading "Zaddikim" has, until  now,  been assigned at  LC  to works  only  about  Hasidic  zaddikim.   The  broader  term   for "Zaddikim" is  "Jewish saints."  The original research for  these headings indicated that the  term zaddik is usually restricted to Hasidism.  "Jewish saints" has been assigned to works on some  of the North African zaddikim.
 
I would question now the exclusivity of using "Zaddikim" only for Hasidim, in light  of  the  fact  that  the  term  has  a generic
Talmudic meaning  and  has  also appeared in  the  North  African context.   In   the  Bar-Ilan  Subject  Headings,  a  scope  note specifies  that  "Zaddikim"  are   not   limited   to   Hasidism. Furthermore, there  doesn't  seem  to  exist literary warrant  to justify retaining "Jewish saints."  Therefore, LC has canceled  "Jewish  saints"  and  added  it  as   a  reference  to
"Zaddikim."   Also,  LCSH  allows  for geographic subdivision under "Zaddikim."
 
As for the  relation  of  the heading  "Miracle  workers"  to  that  of  "Zaddikim."   "Miracle workers" is not limited to the religious context and, in fact, is not linked at all to  to the heading "Saints."  While there is no doubt that Zaddikim are often considered to be doers of nifla'ot, I don't think that a link may be made to "Zaddikim."