The replacement can be
<sup>$0</sup>
or
<sup>$&</sup>
Note that the $0
/ ${0}
/ $&
, or even $MATCH
and ${^MATCH}
backrefrence inserts the whole match.
See the Substitutions section:
$&
,$MATCH
,${^MATCH}
The whole matched text.
and
$n
,${n}
,\n
Returns what matched the subexpression numbered n. Negative indices are not alowed.
Note that a match value is usually stored as Group 0 inside a match object.
However, \0
as of now does not work (Notepad++ v.6.9), it looks like it is treated as a NUL character and truncates the replacement pattern right at the location where it is located.