How do I convert accented letters to normal letters using Application Composer?

You can use the Regex function or use code to validate whether a field contains accented characters.

If found, you can then use Contain function and substringBefore and substringAfter to break the string and replace the value as required.

Here's a sample code that shows an error message if the field contains any of the (! @ #) characters.

Vector a = new Vector ()
a.add('!')
a.add('@')
a.add('#')
//add lines with the characters to be blocked according to the requirement
for (int i=0; i < newValue.length();i++)
{
if (a.indexOf(newValue[i]) >= 0)
    {
      return false
    }
}
return true