Docu update.

doc/tex/mod/Setpartab

@@ -37,6 +37,7 @@ The following parameter table entries are supported:
  convert         & INTEGER     & Set to 1 to convert the unit if necessary
 @EndTable
 
+Unsupported parameter table entries are stored as variable attributes.
 The search key for the variable depends on the operator. Use @oper{setpartabn} to search variables by the name.
 This is typically used for NetCDF datasets. The operator @oper{setpartabp} searches variables by the parameter ID.
 @EndDescription

src/operator_help.h

@@ -884,6 +884,7 @@ static const char *SetpartabHelp[] = {
     "     delete          & INTEGER     & Set to 1 to delete variable",
     "     convert         & INTEGER     & Set to 1 to convert the unit if necessary",
     "    ",
+    "    Unsupported parameter table entries are stored as variable attributes.",
     "    The search key for the variable depends on the operator. Use setpartabn to search variables by the name.",
     "    This is typically used for NetCDF datasets. The operator setpartabp searches variables by the parameter ID.",
     "",