Notepad++ find and replace within a constant string

You can do it following these steps:

• open find and replace dialog (CTRL+H)
• make sure "regular expression" box is checked
• find what:
  \\textbf\{([^}]*)\}
• replace to:
  $1

You can test is here

An alternative approach is to use a non-greedy wildcard (.*?) in the capturing group.

Search for:

\\textbf\{(.*?)\}

Replace with:

\1