BUG Report
(1) InDesign Beta 18.9
(2) Cursor in text block or selected text --> Click on Paragraph Sales drop-down field
(3) See a listing of all of your styles , at least showing 15, 20 etc. with a list that dropdowns the entire screen
(4) Sometimes it display a small window showing only 5 or so styles at a time, other times, a larger window with slightly more styles and sometimes, a large window showing all of your styles.

Behavior is inconsistent, showing a large window with a full list sometimes and a smaller window other times.