I would use a two step process.
First use Match Pattern to look for the string:
Bootloader\s=\s
Make sure that you have enabled slash codes in the regular expression string constant so you can see the spaces.
Next do a search on the string after the match for the expression:
[\r\n]+
This will match any number of carriage returns or line feeds. The string before the match should be what you are looking for.
Mike...