Well Larry beat me to one answer, so here is my answer
The tag line is displayed using the WordPress function 'bloginfo('description');' so it gets displayed in one line. Now there is another WordPress function 'get_bloginfo();' and you can use 'description' to get the tag line and put it in a variable
HTML Code:
$tag_title= get_bloginfo('description');
and then you could use the 'substr()' function to split it where you want it.
HTML Code:
$tag_title= get_bloginfo('description');
echo (substr($tag_title,0,10) . '\n' . substr($tag_title,11);
and of course if you ever changed the tagline, you would have to edit this code and change the location of the split.
But, since you are going to have to change the code if you change the tagline, why not just replace the code that is getting the tagline, with your tagline. ie.
if you look at bfa_header_config.php lines 205-207 (version 3.5.3) you will see
HTML Code:
if ( $bfa_ata['blog_tagline_show'] == "Yes" ) {
echo '<p class="tagline">'; bloginfo('description'); echo '</p>';
}
you could change it to
HTML Code:
if ( $bfa_ata['blog_tagline_show'] == "Yes" ) {
echo '<p class="tagline">tagline part 1<br>tagline part 2</p>';
}
This way you even save a little processing since you are not calling another function.