Description
^(?=(?:(?:(\S+))\s+){4})(\S+-)01(?=\s)

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This regular expression will do the following:
- Look ahead and capture the value in COL4 into capture group 1
- Match the leading characters in COL1 upto the last -01
- Replaces the value in COL1 with the leading characters followed by the value from COL4
Example
Live Demo
Sample text
Col1                        COL2               COL3       COL4  col5
ABHS-SMH-4OZ-01            EA               CS             12     1
ABHK-SMH-01                EA               CS             24      1
After Replacement
Col1                        COL2               COL3       COL4  col5
ABHS-SMH-4OZ-12            EA               CS             12     1
ABHK-SMH-24                EA               CS             24      1
Explanation
NODE                     EXPLANATION
----------------------------------------------------------------------
  ^                        the beginning of the string
----------------------------------------------------------------------
  (?=                      look ahead to see if there is:
----------------------------------------------------------------------
    (?:                      group, but do not capture (4 times):
----------------------------------------------------------------------
      (?:                      group, but do not capture:
----------------------------------------------------------------------
        (                        group and capture to \1:
----------------------------------------------------------------------
          \S+                      non-whitespace (all but \n, \r,
                                   \t, \f, and " ") (1 or more times
                                   (matching the most amount
                                   possible))
----------------------------------------------------------------------
        )                        end of \1
----------------------------------------------------------------------
      )                        end of grouping
----------------------------------------------------------------------
      \s+                      whitespace (\n, \r, \t, \f, and " ")
                               (1 or more times (matching the most
                               amount possible))
----------------------------------------------------------------------
    ){4}                     end of grouping
----------------------------------------------------------------------
  )                        end of look-ahead
----------------------------------------------------------------------
  (                        group and capture to \2:
----------------------------------------------------------------------
    \S+                      non-whitespace (all but \n, \r, \t, \f,
                             and " ") (1 or more times (matching the
                             most amount possible))
----------------------------------------------------------------------
    -                        '-'
----------------------------------------------------------------------
  )                        end of \2
----------------------------------------------------------------------
  01                       '01'
----------------------------------------------------------------------
  (?=                      look ahead to see if there is:
----------------------------------------------------------------------
    \s                       whitespace (\n, \r, \t, \f, and " ")
----------------------------------------------------------------------
  )                        end of look-ahead
----------------------------------------------------------------------