How do I set WinHelp browse sequences?

There are two properties in the Topic object on the WinHelp tab which control the browse sequence settings:

Include in browse sequence	When checked, the topic is included in a browse sequence. If unchecked the topic is skipped.
Start new browse sequence	When checked, the topic becomes the beginning of a browse sequence

Topic - Help Tab

The default Chapter Template has start new browse sequence checked. If you wish to start a browse sequence mid-chapter, create a new topic template similar to your "Normal Template" but with "start new browse sequence" checked. Call it something like "Normal (start browse seq)". Using this new template on a mid-chapter topic will start a new browse sequence mid chapter.