Keystroke: j from Layout Menu
This menu selection should be used only when you have highlighted more than one line of text. When you join styles, DBT combines all paragraphs selected or partially selected into a single Linear Style, with only a hard return code between each paragraph.
This feature can be helpful for quickly cleaning up the formatting of text. For example, try applying the 'list.' linear style to the first of a series of paragraphs. Now select at least part of this paragraph and several paragraphs following. Choose Layout: Join Styles, and you have combined all the paragraphs into a single list.