To obtain the desired result, you'll need to capture the number
in a _subpattern_ by enclosing that part of your Find pattern in
parentheses (\d+) so:
Find: \[(\d+)\]
and then insert the matched number by referencing the first (and
only :-) subpattern \1 in your Find pattern:
Replace: \\textsuperscript{\1}
and that should do the job.
[PS: For much more info about creating and using grep patterns,
please see Chapter 8 of the included PDF manual, which you can
access at any time via Help -> User Manual.]
Regards,
Patrick Woolsey
==
Bare Bones Software, Inc. <
http://www.barebones.com/>