If you want a button side by side with the title and tagline, without “plus” and its ability to create variable width widgets in any content area, you will have to code the containers yourself with divs.
It will look something like
<div style=”width:80%;float:left;”>
[site_title matchtheme=true]
[site_tagline matchtheme=true]
</div>
<div style=”width:20%;float:left;”>
Your Button HTML
</div>